Tool List- www.amazon.com/shop/acservicetech Support- www.patreon.com/acservicetech For those that are looking for the tools used in the videos: (Linked Below) Here is the Link for the newer UEI DL469 Multimeter- amzn.to/2jw4ePJ Here is a link for the Supco Magnet Jumpers amzn.to/2gS4h6z Here is the Link for the newer UEI DL479 Multimeter with temp sensor- amzn.to/2jtsUbJ Here is a link to the 24v Thermostat used in the video- amzn.to/2bDeUak Here is the Link for the UEI DL389 Multimeter used in the video - amzn.to/2naJr9o Here is the Link for the FieldPiece ST4 Dual Temp Meter- amzn.to/2AhR6ph Here is the Link for the UEI Temp Sensor- amzn.to/2kawAmJ Here is the link for the Irwin Wire Stripper/Cutter/Crimper- amzn.to/2dGTj2V Here is a link to the Stanley 6 in 1 screwdriver- amzn.to/2x7NuaZ Other tool links can be found in the video description section. ACSERVICETECH is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon. All of the ACSERVICETECH Playlists- ruclips.net/channel/UCOZR-1IqsAer9wzlvFgb4mAplaylists?view_as=public If you want to support the ACSERVICETECH Channel and receive more HVACR content, check out www.Patreon.com/acservicetech
Thank you so much for this video. I had 28 volts at the unit but only 17 at the thermostat so my thermostat wouldn't run unless it had batteries in it. When I looked at the wiring the builders never hooked up the common wire inside the unit that runs to the thermostat. Once I connected that it fixed everything!
If you want to support the ACSERVICETECH Channel and receive more HVACR content, check out www.Patreon.com/acservicetech All of the ACSERVICETECH Playlists- ruclips.net/channel/UCOZR-1IqsAer9wzlvFgb4mAplaylists?view_as=public
Thank you! My replacement thermostat was expecting 'C' connection, but my existing thermostat did not have C, but there was wire available, but not connected. I opened the HAVC and connecting the 'C' wire, and connected the new thremostat- but it was not working - I though i blew the fuse. After seeing your video, I realized it is the auto-shutoff safety switch!! once i put the panel back on it started working again. Thank you very much!
hi, at 4:10 with the face plate pulled off. I you were to measure continuity between R and Y/W/G would your meter beeps? If so why? thank you for your help.
I have a question for somebody that does heating and Air I have three thermostats I have hooked up and neither one of them want to work right without wires hooked to I don't get any continuity from the red to the white on the heating cycle is it not supposed to be that way or what's going on can somebody answer that
Jeremy Caswell I would just jump the wires then , use a jumper or tie the R n G wires together and see if the fan turns on , that will let u know if the thermostat is bad too ..... I’m still in school so idk , but that’s what I do
Why is it that i ONLY get 24V between Common/Blue - and Red + when the unit is ON ... Once the ac turns OFF, i loose that 24V connection until the unit turns back on ... Isn't there supposed to be 24V there all the time whether or not the unit is ON or OFF ??
I see a lot of furnaces and thermostats that don't have a common wire. If I want to check for a call for heat on th furnace control board, do I put my leads on R and W and hope for a reading of zero on my meter?
Different appliance not sure if you can help....I am burning up relays on a pcb for a wine cooler...it has a compressor and is basically just like a refrigerator....I am having an issue with low voltage at the pcb relay ..I get the constant 12v supply but not getting a good ground on the other side of coil...I measure 6 volts across the coil.... I took a look at the board and the drive circuit for the grounding of the relay and I can't seem to find anything that really stands out other than the transistor base only receiving .5v......it should receive .7v You ever hear of a thermostat having some type of resistance issues or problems in the thermostat itself that is sending a good enough signal to close the relay contacts and operate the compressor but not a good enough voltage to get the relay to operate as it's supposed to? I could just have a transistor issue but I don't know enough about pcb components to diagnose transistors....I'm just seeing that .5v and I know that number is low
Thank you for the great video. I have only two wires coming to my thermostat, connected to R and W. The voltage measures 77 V-AC. The thermostat is rated (like most other thermostats) at 24 AC and it has no issues. What puzzles me is how can you get voltage between a wire that is supposed to have 24 AC (attached to terminal R) and the wire going to terminal W, which I believe, is supposed to complete the circuit of the zone valve, thereby turning the boiler on?! I thought one can measure the 24 V line with the other probe attached to a common wire/terminal only! Your comments are appreciated in advance. Zack
Quite helpful! I'm untrained in HVAC and thought I'd see 24 VAC between Rh and W when heating - not the W and C as you've measured (makes sense now). I have a gas fireplace (mV system) where an existing Honeywell connected Rh and W to replace what was previously a manual 'light' switch. To hook up my Sensi WiFi thermostat, I'm thinking of two options: (1) de-jumper Rc and Rh and wire Rc and C to the 24 VAC supply (for the thermostat to use), then wire Rh and W like the Honeywell it replaces. Seems easiest, but I'm not convinced the right way because there may have been a setting inside the Honeywell allowing it to support millivolt systems which my Regency P42 is. Option (2) is to wire W and C to a 24 VAC relay simulating the fireplace on/off switch. You make the point in another reply that current is flowing through Rh and W, so it sounds dangerous to use the thermostat's internal relay as a switch - I'll check the Honeywell manual if there was a setting to de-energize it on that one but the Sensi manual simply says "millivolt systems are not supported."
The common is the path back for voltage. It is needed to check for true potential voltage. A ground can be used as well to check for a hot wire. In order to power a load, the voltage is carried to the component via the hot wire and back to the power source via the common wire, thanks
What do you mean by a ground can also be used to check for a hot wire? Another question: Are you the one selling the multimeter on amazon? If so, I would like to buy through you.
One probe would go on the hot wire and one probe would go on the ground to check for voltage. We would typically check one probe on hot and one on common to check for voltage. Make sure you are working with a licensed professional when working on any electrical for safety. I am not the one selling the multimeter on amazon but check the stars on the particular company. I do receive a decent commission on each sale though. It is just a way in order to try to help make all of this free training financially sustainable. Any time someone enters any link I have provided, I will receive a commission which is referred to as an advertising fee even if some other unrelated item is purchased since the individual entered amazon through my link. The link must be clicked through here on youtube and not cut and pasted. Prices are the same as normal and I usually have the tool links in the description section of the videos. Here is a link to check out tools that I use- www.amazon.com/shop/acservicetech
acservicetech Thank you! It's always confusing with neutral, ground and common. So what your saying is what goes in has to come back to complete the circuit?
So when the tstat finally calls for cooling and only the IDM runs with no condenser unit. No voltage from y to c. Only y to g. Checked secondary overflow switch(dry), pressure switches at condenser unit.( pressure in system). Could this mean tstat is defective?
Tested two tstats and both had same issue, no 24v at board on y to common. Then i put the original tstat they had back on and works fine. Defective tstats?
I don’t get it. When my face plate is off, there is NO voltage anywhere on the pins, but yet my thermostat works when it is snapped back on. I see that your blue wired is on the C connector. You called it the common wire. Is this the same as the ‘C’ wire? I’d like to replace my thermostat with a newer model that requires a c-wire (a blue) but I can’t get any voltage readings.
Sir how does it works...how it controls fan motor speed in 3 speeds...my single phase fcu motor has 3 wires....low ,medium,and high... Without thermostat ,I just tried to connect live(230v) wire to low speed winding...no power trip... But if I connect live wire to medium and high speed windings.power is getting trip...what is the reason sir... without thermostat how I can run the motor in high speed?pls help me .
Wouldnt it be less confusing to test the mode its in (ie cooling), from Y to R? Then the reading is more simple (with power applied): a closed switch = 0 volts; an open switch reads = 24 V
thats exactly what threw me off too i was testing my control board and found the multimeter read 24v when it was calling for heat so i thought the thermostat was in open circuit
Still throws me off till this day. Gotta take a step back & gather my thoughts sometimes lol such a simple thing that can be over complicated if overthought
You wouldn't connect the 24v r power wire with the C common wire. You would measure with the multimeter probes from those two spots to measure for 24v thanks!
Why is there a 24 V reading across switches that are closed in a thermostat But when measuring voltage across a light switch for example, a 24 V reading would mean switch open?
There wouldn't be 24v between two terminals that were touching because the meter is reading the potential difference in voltage. You would measure from C to a hot to read 24v, thanks!
Have a question? I have a split system at work that is freezing up. The refrigerant is good and I put on a new defrost board also new filter, cleaned unit and it is still happening. Could you give me some advice please.
Have you tried to force defrost and make sure that it is capable and not going out on a limit or something in the middle of defrost. Typically defrost is for ten minutes unless a dft sensor is equipped and senses the temp is high enough. You could also set the timer on the board for a shorter period of time so it goes into defrost sooner. Let me know what you find or how you make out Keith, thanks!
I tested my wires and my multi meter read zero. Does that mean I have bad wires or is there something bad with my furnace that it is connected to. My power to my home did go out and cause 2 power strips to go bad, could that have caused the problem with the wires?
You would have to test at the furnace to see if you have 120v in and 24v when putting the meter probes between r and c. If the board has an led then it should be lit up unless there is no power or the fuse is blown, thanks!
Good clip, so the blue common ,only provides a neutral to the thermostat. Is that correct.The Yellow goes out to the outside contractor, but what is the other side( the neutral).Is that the neutral coming off the transformer ? Thanks
In the winter (about 4-5 months ago) my outside AC compressor was coming on when the furnace was on. I turned the AC circuit breaker off to turn the power off to the compressor as there was no other way to stop it from running w/the heater. (I figured I'd deal with it in the springtime. Now that it is getting hotter outside, I went to use the AC yesterday and neither the blower fan motor or compressor is coming on (will not work even in HOLD mode). If I switch the thermostat back to heater mode, the heater works fine. Is this likely a thermostat problem? The thermostat is a program-able Ritetemp model 8022C. Any ideas would be deeply appreciated. Also, I do have a voltage meter to test if I know the procedure. I would guess 24 volts. THX.
my RV is of the Year 2009 and has the problem that I turn on the air at less temperature and it works a couple of seconds and it turns off, what can it be? ... I already clean it completely and follow the problem!
Hey i got a question; why in one of your older video about checking a thermostat; you said do not to check voltage between Red and Common terminals because it can blow the fuse o burn the transformer? And here you are doing it? Did you mean not to jump red and common? Or checking voltage between red and common? Can you please elaborate on that? Just asking for a friend!
HI A.C I just bought a UEI DL 489 metre , But its giving me wierd Amp readings. For example when I turn on the metre it reads 0.4 -0.8 Amp and doesn't zero out . Also the readings are inconsistent with the rating plate or if i get a reading and after I un hook from my wire the reading stays on the screen . should I return it to my supply house for a new one or in your opinion what would be a better choice of metre for the price I paid for the UEI . I spent just shy of 400 CAD .
Wow I think I only ever heard of that happening once before with a weird amp reading. We have 12 of the dl389 at the shop and I also have had one for many years. No problems. They were $130. I am now also using the DL479 and they are $80. I would certainly return it and at least get another. Sorry to hear that Sean! I use the dl389 and dl479 for everything and would stick with UEI personally.
It is either the program setting such as it being set on "fan on" instead of "Fan auto" or it is possible that the g wire is touching the r wire, thanks!
does it matter which probe you put where? because i figure that black would go to common and red goes to everything else. i gues it only matters when black needs to be put to a ground.
I'm curious if you're testing on an actual unit or if you have some type of demo panel built. I'm looking to build one to test thermostats using battery power. Any suggestions?
This isn't a demo panel but just a board with a transformer and tstat. If you are just testing the connections then use the ohm function between the wires as they exit the tstat when powering the tstat with batteries. I believe one of my heat pump tstat troubleshooting videos was shown like that, thanks
I'm troubleshooting my new Nest Thermometer. I'm having to remove the Common wire from the Nest to make it work so I am troubleshooting what is going on. If I measure the voltage from R to C I get 0 volts. This is at the circuit board on the unit. I just ran a new thermostat wire(to get the "C" wire) several weeks back preparing for a new Nest.
@@acservicetechchannel I was a dummy. #1. I had the switch "off" to the unit when I was testing voltage. Big DUH. #2 found the issue. When I connected the new Thermostat wiring the installers had used a short jumper inside the handler in the attic. Originally the "Common" wire was not connected. So rather than running my new thermostat wiring to the circuit board I simply connected to the short jumper. So the "Common" wire connection was new on the jumper. Well turns out the new lead broke underneath the wire nut so the "Common" wire was not actually connected from the new Nest Thermostat to the circuit board in the handler. I guess the Nest was smart enough to notice and simply suggested removing the "Common" wire connection since it was doing nothing. Working fine now that I fixed the broken lead.
This is a great video. Thanks! Question: my thermostat has died (I still have power to the display but no response in the buttons and no response when trying to reset it). I want to test to make sure I'm still getting power to the thermostat from the furnace so I can temporarily jump it until I get my new thermostat. It's a White Rodgers (now Emerson) 1F78. This only has RC and RH (not a separate common or R) so do I use the multimeter on RH and on W (to test heat) or is it RH to RC? Also I can't get the magnetic cable you feature but I can get the Supco MAG1BL which is also up to 30 vac. Will this work? Thanks again! Edited to add more detail.
The free heat I get from my apt. complex isn't enough for me sometimes, and I'll put some ice around the thermostat. This trick used to work big time, but now it doesn't work at all. Have complexes gotten wise to this trick, and devised a way to prevent a sudden drop in temperature from being taken seriously? The thermostat will say the heat is on when I do this, but the baseboard heaters stay cold. But if I remove the ice, and the temperature returns to normal, the heaters will come on naturally from a natural drop in temperature. Does anyone have any thoughts on this, and what I can do to fix it?
why dont you have an extra wire on Y and common on furnace control board going out to the outdoor condensing unit? p.s you've taught me so much from your videos i hope to help you out on patreon as soon as i finish my 6 week training for becoming a service technician
Thank you very much Omar. There are around 40 articles on there too at patreon.com/acservicetech On that video I just don't think I had it wired. Good observation!
Hi this is Blaze from SoCal again. You are up early. I have a question. I do all commercial. I also only carry Ventstar 2800's thermostats on my truck. Recently I had a problem with a stat. When I got a call for heat the reversing valve did not de energize. I was working on a Trane Voyager. I jumped across the test pins and the unit went through all operations. The units okay. I removed the thermostat from the wires and jumped out the unit there apart from the stat. The unit heated and cooled. Bad stat? I replaced the thermostat with the same result. I know my low voltage wire is okay but I still checked it out. I then replaced my low voltage wire at the unit with new and attached another T2800 to it with the same result. I'm pulling my hair out by now. Anyways I went to my vendors and picked up a Honeywell 6000 and am going to try again tomorrow. Any suggestions? Thank you again for a great video!
Do you have the reversing valve switched from B to O? R powers to B in cooling mode and R powers to O in heat mode. These are for the reversing valve depending on if the unit powers the reversing valve in heat or cooling. When you said you tested the system with the tstat wires disconnected from the tstat, I am assuming you already wire nutted the correct wires together to get heat right? thanks Blaze! Yeah in reference to the time you saw the video was uploaded at, that seems to be the only tim e to try to get them done. The kids go to sleep at 8 and I work on a video from 4-5 hours to get it done edited, and all the rest, ha ha thanks
acservicetech Thank you again for the great videos. Ahh to be young again. I'm in bed by 9 at the latest and then up at 2:45 the next morning. Regarding the thermostat issue. Both of the T 2800's that I used would not de energize the coil when I went to the heating mode. I installed a Honeywell 6000 and it controlled my unit correctly. I took the 2800's back to SIGLER for warranty. Thank you for the reply. Merry Christmas to you and your family!
that is an awesome tutorial there partner! how can I subscribe to the channel you talk about? I want to learn more advanced troubleshooting and other task that are not on the tube?????
So I have about 20 community level posts there and more to come but it is also for those who want to ask more questions and a way for those who choose to support the channel here. Check out the video I made to explain it at the top of the screen at Patreon.com/acservicetech Also so you know, I am in the process of writing a book. Thanks as always!
The heat on the thermostat will not turn on without me turning it off then on again or going one degree below room temperature then back above room temperature. Why is that ? I can put the temperature to 76 but it won’t turn on only if I do those steps . It’s on heat and auto but will not turn on unless I do those steps. It’s a new thermostat
I had a new HVAC system installed last year and a honeywell stat that has 4 wire running to it.(no C wire). The system when in A/C mode will set there and run until I turn the stat up, but I have to turn it up 3 or 4 degrees or the temperature reading will jump a degree or 2 to match where I set it to. I know sounds crazy. It will also jump down and match within a degree or 2. SO... first I called honeywell thinking this must be a stat issue. They had me test the voltage readings of the 4 wires running to the stat. The 24v red was fine but one of the wires read lower like 9v and seemed to vary. Honeywell blamed the HVAC system as the problem. So I called the HVAC tech out and after thinking it was the wires running to the stat he checking the voltage readings at the unit with the stat wires removed, he got the same readings ( one circuit was low and varied) eliminating the wires to the stat as the issue. He then said it was an ECM module/motor.He did a warranty replacement of the ECM and said it's fixed. For some reason this issue takes a few hours before it acts up. Then the longer it runs the worse it gets. He finished the warranty repair and said even though the voltage is still low in one circuit the system was working fine, but the next day it did the same thing. I replaced the Honeywell stat again and it does the same thing also. Any ideas what I should do?
Hey jimbola77, I finally go the paypal account set up. They had a hard time linking to the account. Anyway it is now set up for anyone that wants to contribute to the ongoing work of the channel instead of through Patreon- www.paypal.me/acservicetech - Thanks for your consideration either way and as always, let me know if you have any HVACR questions, thanks
I know this is super late, just in case someone else is having this question. When you are taking voltage across two points in a circuit, you are reading the difference between the two point. The C terminal is a straight connection to the C side of the transformer. The R side of the transformer is what is being switched by the thermostat to the W, Y, and G terminals to make the various calls. We see voltage because R and C are 27 volts RMS apart from each other. If you were to read from R to Y, and there is a call for cooling, then you would read 0 volts because the voltage is the same across those two points.
Tool List- www.amazon.com/shop/acservicetech
Support- www.patreon.com/acservicetech
For those that are looking for the tools used in the videos: (Linked Below)
Here is the Link for the newer UEI DL469 Multimeter- amzn.to/2jw4ePJ
Here is a link for the Supco Magnet Jumpers amzn.to/2gS4h6z
Here is the Link for the newer UEI DL479 Multimeter with temp sensor- amzn.to/2jtsUbJ
Here is a link to the 24v Thermostat used in the video- amzn.to/2bDeUak
Here is the Link for the UEI DL389 Multimeter used in the video - amzn.to/2naJr9o
Here is the Link for the FieldPiece ST4 Dual Temp Meter- amzn.to/2AhR6ph
Here is the Link for the UEI Temp Sensor- amzn.to/2kawAmJ
Here is the link for the Irwin Wire Stripper/Cutter/Crimper- amzn.to/2dGTj2V
Here is a link to the Stanley 6 in 1 screwdriver- amzn.to/2x7NuaZ
Other tool links can be found in the video description section.
ACSERVICETECH is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.
All of the ACSERVICETECH Playlists- ruclips.net/channel/UCOZR-1IqsAer9wzlvFgb4mAplaylists?view_as=public
If you want to support the ACSERVICETECH Channel and receive more HVACR content, check out www.Patreon.com/acservicetech
acservicetech has
could u connect more than 1 wire to the common wire?
😊
For the novice they'll would want to know if the red probe goes on the red
Your camera didn't get that part
Thank you so much for this video. I had 28 volts at the unit but only 17 at the thermostat so my thermostat wouldn't run unless it had batteries in it. When I looked at the wiring the builders never hooked up the common wire inside the unit that runs to the thermostat. Once I connected that it fixed everything!
Wonderful video. An oldie but goodie.
Nice video, Craig. Those mag jumpers are pretty cool.
Thanks Jack!
Thanks for the video. Question: how to measure the volts if there is no C wire?
R and Y wires is 24 volts AC. Also R and W is 24 volts and R and G is 24 volts...using a voltmeter.
One of the best I've seen! My problem is that 24VAC no longer present between R and C...
Did you find a solution for this?
Calling for cool, Red to yellow, turns on the fan WITHOUT jumping to the green also?
If you want to support the ACSERVICETECH Channel and receive more HVACR content, check out www.Patreon.com/acservicetech
All of the ACSERVICETECH Playlists- ruclips.net/channel/UCOZR-1IqsAer9wzlvFgb4mAplaylists?view_as=public
What if I'm getting a 118 V on the red and common thermostat?
Thank you! My replacement thermostat was expecting 'C' connection, but my existing thermostat did not have C, but there was wire available, but not connected. I opened the HAVC and connecting the 'C' wire, and connected the new thremostat- but it was not working - I though i blew the fuse. After seeing your video, I realized it is the auto-shutoff safety switch!! once i put the panel back on it started working again. Thank you very much!
If there's no heating or cooling, do i need to do the jumps in the thermostat only or in the control board, too? Thanks
Thanks for reminding me that my panel has a door switch! I could NOT figure out why my a/c unit wouldn’t turn on after I removed it!
Glad to help Michael!
hi, at 4:10 with the face plate pulled off. I you were to measure continuity between R and Y/W/G would your meter beeps? If so why? thank you for your help.
You wouldn't measure continuity because voltage is going through. You would test in voltage with C, thanks
Great job and video
Thanks for the visit
Thanks. This is very useful.
Glad it was helpful!
When u put it heat mode in auto should the W and G get power or just W?
Thank you! Great vid, it worked to trouble shoot a problem at work
I have a question for somebody that does heating and Air I have three thermostats I have hooked up and neither one of them want to work right without wires hooked to I don't get any continuity from the red to the white on the heating cycle is it not supposed to be that way or what's going on can somebody answer that
I also jumped the wires red and white together and the furnace works but with the thermostat it does not
@@robertpoteet6324 if you jumped the red (24V) to the white (heat) and it kicks ON, that means something is wrong with the thermostat
These are very good videos. Very informative
Thanks William!
Can I read voltage by probing white and a good metal that's not the common terminal
I only have 12.5 volts when checking W terminal at furnace board does that mean I have a bad thermostat
Great, cleared up some gray areas I had. THANKS FRIEND
Thanks Ronald!
What do you check for 24 volts with if there is no common. As in no wire and no clear connection on the board
Jeremy Caswell I would just jump the wires then , use a jumper or tie the R n G wires together and see if the fan turns on , that will let u know if the thermostat is bad too ..... I’m still in school so idk , but that’s what I do
Is my thermostat bad my furnace won’t turn on but if I reset power on furnace it turn on
Great video 👍
Thanks Jamie!
Why is it that i ONLY get 24V between Common/Blue - and Red + when the unit is ON ...
Once the ac turns OFF, i loose that 24V connection until the unit turns back on ...
Isn't there supposed to be 24V there all the time whether or not the unit is ON or OFF ??
I see a lot of furnaces and thermostats that don't have a common wire. If I want to check for a call for heat on th furnace control board, do I put my leads on R and W and hope for a reading of zero on my meter?
You would still put your meter lead on the c terminal and the w terminal on the control board even if the thermostat does not use a common, thanks
Different appliance not sure if you can help....I am burning up relays on a pcb for a wine cooler...it has a compressor and is basically just like a refrigerator....I am having an issue with low voltage at the pcb relay ..I get the constant 12v supply but not getting a good ground on the other side of coil...I measure 6 volts across the coil....
I took a look at the board and the drive circuit for the grounding of the relay and I can't seem to find anything that really stands out other than the transistor base only receiving .5v......it should receive .7v
You ever hear of a thermostat having some type of resistance issues or problems in the thermostat itself that is sending a good enough signal to close the relay contacts and operate the compressor but not a good enough voltage to get the relay to operate as it's supposed to? I could just have a transistor issue but I don't know enough about pcb components to diagnose transistors....I'm just seeing that .5v and I know that number is low
Thank you for the great video. I have only two wires coming to my thermostat, connected to R and W. The voltage measures 77 V-AC. The thermostat is rated (like most other thermostats) at 24 AC and it has no issues. What puzzles me is how can you get voltage between a wire that is supposed to have 24 AC (attached to terminal R) and the wire going to terminal W, which I believe, is supposed to complete the circuit of the zone valve, thereby turning the boiler on?! I thought one can measure the 24 V line with the other probe attached to a common wire/terminal only!
Your comments are appreciated in advance.
Zack
Quite helpful! I'm untrained in HVAC and thought I'd see 24 VAC between Rh and W when heating - not the W and C as you've measured (makes sense now). I have a gas fireplace (mV system) where an existing Honeywell connected Rh and W to replace what was previously a manual 'light' switch. To hook up my Sensi WiFi thermostat, I'm thinking of two options: (1) de-jumper Rc and Rh and wire Rc and C to the 24 VAC supply (for the thermostat to use), then wire Rh and W like the Honeywell it replaces. Seems easiest, but I'm not convinced the right way because there may have been a setting inside the Honeywell allowing it to support millivolt systems which my Regency P42 is. Option (2) is to wire W and C to a 24 VAC relay simulating the fireplace on/off switch. You make the point in another reply that current is flowing through Rh and W, so it sounds dangerous to use the thermostat's internal relay as a switch - I'll check the Honeywell manual if there was a setting to de-energize it on that one but the Sensi manual simply says "millivolt systems are not supported."
Ca you explain the common wire? Can you test from R to Y and get the same result? What exactly does the common wire do?
The common is the path back for voltage. It is needed to check for true potential voltage. A ground can be used as well to check for a hot wire. In order to power a load, the voltage is carried to the component via the hot wire and back to the power source via the common wire, thanks
What do you mean by a ground can also be used to check for a hot wire?
Another question: Are you the one selling the multimeter on amazon? If so, I would like to buy through you.
One probe would go on the hot wire and one probe would go on the ground to check for voltage. We would typically check one probe on hot and one on common to check for voltage. Make sure you are working with a licensed professional when working on any electrical for safety. I am not the one selling the multimeter on amazon but check the stars on the particular company. I do receive a decent commission on each sale though. It is just a way in order to try to help make all of this free training financially sustainable. Any time someone enters any link I have provided, I will receive a commission which is referred to as an advertising fee even if some other unrelated item is purchased since the individual entered amazon through my link. The link must be clicked through here on youtube and not cut and pasted. Prices are the same as normal and I usually have the tool links in the description section of the videos. Here is a link to check out tools that I use- www.amazon.com/shop/acservicetech
acservicetech
Thanks a lot.
Do you have a Facebook page?
acservicetech Thank you! It's always confusing with neutral, ground and common. So what your saying is what goes in has to come back to complete the circuit?
This channel is so great ! Thank you
Thanks Tristan C!
Thank you! 😊
So when the tstat finally calls for cooling and only the IDM runs with no condenser unit. No voltage from y to c. Only y to g. Checked secondary overflow switch(dry), pressure switches at condenser unit.( pressure in system). Could this mean tstat is defective?
Started with a blown fuse. Replaced. Then only the idm runs. Checked for continuity(good) even stripped back clean wire for terminals.
Tested two tstats and both had same issue, no 24v at board on y to common. Then i put the original tstat they had back on and works fine. Defective tstats?
Video was very helpful.
Thanks Shawn!
I don’t get it. When my face plate is off, there is NO voltage anywhere on the pins, but yet my thermostat works when it is snapped back on. I see that your blue wired is on the C connector. You called it the common wire. Is this the same as the ‘C’ wire? I’d like to replace my thermostat with a newer model that requires a c-wire (a blue) but I can’t get any voltage readings.
Mine has 10 volts..what would be the problem..heat or ac not tuening on at all
Thanks! I've tested these and they are fine, my issues is that heat stops shy of set temperature. Could it be the thermostat?
Sir how does it works...how it controls fan motor speed in 3 speeds...my single phase fcu motor has 3 wires....low ,medium,and high...
Without thermostat ,I just tried to connect live(230v) wire to low speed winding...no power trip...
But if I connect live wire to medium and high speed windings.power is getting trip...what is the reason sir... without thermostat how I can run the motor in high speed?pls help me
.
Wouldnt it be less confusing to test the mode its in (ie cooling), from Y to R? Then the reading is more simple (with power applied): a closed switch = 0 volts; an open switch reads = 24 V
thats exactly what threw me off too i was testing my control board and found the multimeter read 24v when it was calling for heat so i thought the thermostat was in open circuit
Still throws me off till this day. Gotta take a step back & gather my thoughts sometimes lol such a simple thing that can be over complicated if overthought
always good technical teaching, thank you ...
thanks
Would this be the same process if it was a package unit?
Yes one that is 24v ac voltage based, thanks!
wouldn't you short out the transformer or something else if you connect the red terminal whit the common one?
You wouldn't connect the 24v r power wire with the C common wire. You would measure with the multimeter probes from those two spots to measure for 24v thanks!
Thank you for the video. Can I hook my step down transformer 240v to 24v straight to my thermostat wire to t stat
Hey guys im in the market for a meter is this UEI meter good and reliable?
Why is there a 24 V reading across switches that are closed in a thermostat
But when measuring voltage across a light switch for example, a 24 V reading would mean switch open?
There wouldn't be 24v between two terminals that were touching because the meter is reading the potential difference in voltage. You would measure from C to a hot to read 24v, thanks!
Have a question? I have a split system at work that is freezing up. The refrigerant is good and I put on a new defrost board also new filter, cleaned unit and it is still happening. Could you give me some advice please.
Have you tried to force defrost and make sure that it is capable and not going out on a limit or something in the middle of defrost. Typically defrost is for ten minutes unless a dft sensor is equipped and senses the temp is high enough. You could also set the timer on the board for a shorter period of time so it goes into defrost sooner. Let me know what you find or how you make out Keith, thanks!
acservicetech ok will do
I tested my wires and my multi meter read zero. Does that mean I have bad wires or is there something bad with my furnace that it is connected to. My power to my home did go out and cause 2 power strips to go bad, could that have caused the problem with the wires?
You would have to test at the furnace to see if you have 120v in and 24v when putting the meter probes between r and c. If the board has an led then it should be lit up unless there is no power or the fuse is blown, thanks!
Good clip,
so the blue common ,only provides a neutral to the thermostat. Is that correct.The Yellow goes out to the outside contractor, but what is the other side( the neutral).Is that the neutral coming off the transformer ? Thanks
Yes, it connects to the blue that can be used as the common for the thermostat, thanks
In the winter (about 4-5 months ago) my outside AC compressor was coming on when the furnace was on. I turned the AC circuit breaker off to turn the power off to the compressor as there was no other way to stop it from running w/the heater. (I figured I'd deal with it in the springtime.
Now that it is getting hotter outside, I went to use the AC yesterday and neither the blower fan motor or compressor is coming on (will not work even in HOLD mode). If I switch the thermostat back to heater mode, the heater works fine. Is this likely a thermostat problem? The thermostat is a program-able Ritetemp model 8022C. Any ideas would be deeply appreciated.
Also, I do have a voltage meter to test if I know the procedure. I would guess 24 volts. THX.
Excellent like always
Thanks Tank!
So if you're set to hear and get 0v across whatever you're set on +Common the Tstat is the problem?
or the tstat wiring if you are reading it at the control board, thanks
As always, great video. Thanks for sharing.
Thanks Dean Martin 1966!
my RV is of the Year 2009 and has the problem that I turn on the air at less temperature and it works a couple of seconds and it turns off, what can it be? ... I already clean it completely and follow the problem!
Hey i got a question; why in one of your older video about checking a thermostat; you said do not to check voltage between Red and Common terminals because it can blow the fuse o burn the transformer? And here you are doing it? Did you mean not to jump red and common? Or checking voltage between red and common? Can you please elaborate on that? Just asking for a friend!
Yes of you jump red and common it could blow your fuse
HI A.C I just bought a UEI DL 489 metre , But its giving me wierd Amp readings. For example when I turn on the metre it reads 0.4 -0.8 Amp and doesn't zero out . Also the readings are inconsistent with the rating plate or if i get a reading and after I un hook from my wire the reading stays on the screen . should I return it to my supply house for a new one or in your opinion what would be a better choice of metre for the price I paid for the UEI . I spent just shy of 400 CAD .
Wow I think I only ever heard of that happening once before with a weird amp reading. We have 12 of the dl389 at the shop and I also have had one for many years. No problems. They were $130. I am now also using the DL479 and they are $80. I would certainly return it and at least get another. Sorry to hear that Sean! I use the dl389 and dl479 for everything and would stick with UEI personally.
Could you make a video on how the common wire works. It would save alot of headaches! Thanks.
At some point I would like to do a video on the transformer, thanks
Sure let me know! Would like to see it.
I have a nest thermostat I have it on cooling as it shuts down the fan constantly keeps running
It is either the program setting such as it being set on "fan on" instead of "Fan auto" or it is possible that the g wire is touching the r wire, thanks!
What if you don't have blue wire connected to the thermostat?
Great video, very informative.
Thanks Wayne!
does it matter which probe you put where? because i figure that black would go to common and red goes to everything else. i gues it only matters when black needs to be put to a ground.
When I switch to heat, it blows the fuse in the control panel
I'm curious if you're testing on an actual unit or if you have some type of demo panel built. I'm looking to build one to test thermostats using battery power. Any suggestions?
This isn't a demo panel but just a board with a transformer and tstat. If you are just testing the connections then use the ohm function between the wires as they exit the tstat when powering the tstat with batteries. I believe one of my heat pump tstat troubleshooting videos was shown like that, thanks
really helpful video thank you!
Thanks Calm Energy!
I'm troubleshooting my new Nest Thermometer. I'm having to remove the Common wire from the Nest to make it work so I am troubleshooting what is going on. If I measure the voltage from R to C I get 0 volts. This is at the circuit board on the unit. I just ran a new thermostat wire(to get the "C" wire) several weeks back preparing for a new Nest.
If you get 0 volts from r to c on the board then the board is not supplying the 24v needed. Maybe the 24v fuse at the board is blown?
@@acservicetechchannel I was a dummy. #1. I had the switch "off" to the unit when I was testing voltage. Big DUH.
#2 found the issue. When I connected the new Thermostat wiring the installers had used a short jumper inside the handler in the attic. Originally the "Common" wire was not connected. So rather than running my new thermostat wiring to the circuit board I simply connected to the short jumper. So the "Common" wire connection was new on the jumper. Well turns out the new lead broke underneath the wire nut so the "Common" wire was not actually connected from the new Nest Thermostat to the circuit board in the handler.
I guess the Nest was smart enough to notice and simply suggested removing the "Common" wire connection since it was doing nothing.
Working fine now that I fixed the broken lead.
This is a great video. Thanks! Question: my thermostat has died (I still have power to the display but no response in the buttons and no response when trying to reset it). I want to test to make sure I'm still getting power to the thermostat from the furnace so I can temporarily jump it until I get my new thermostat. It's a White Rodgers (now Emerson) 1F78. This only has RC and RH (not a separate common or R) so do I use the multimeter on RH and on W (to test heat) or is it RH to RC? Also I can't get the magnetic cable you feature but I can get the Supco MAG1BL which is also up to 30 vac. Will this work? Thanks again!
Edited to add more detail.
Great video thanks for the info
Thanks Keith!
What if you don’t have a C wire?
what if you only have 4 wires? R, W, Y, G. how would you check voltage between the terminals? R to the desired terminal?
Check with the w to c or y to c, or g to c back at the board for 24v to see if the tstat is working, thanks
@@acservicetechchannel : So we have to have a C terminal in order to check the voltages of other terminals, right? Thank you.
R and W is 24 volts AC. Also R and Y is 24 volts and Also R and G ...
The free heat I get from my apt. complex isn't enough for me sometimes, and I'll put some ice around the thermostat. This trick used to work big time, but now it doesn't work at all. Have complexes gotten wise to this trick, and devised a way to prevent a sudden drop in temperature from being taken seriously? The thermostat will say the heat is on when I do this, but the baseboard heaters stay cold. But if I remove the ice, and the temperature returns to normal, the heaters will come on naturally from a natural drop in temperature. Does anyone have any thoughts on this, and what I can do to fix it?
why dont you have an extra wire on Y and common on furnace control board going out to the outdoor condensing unit? p.s you've taught me so much from your videos i hope to help you out on patreon as soon as i finish my 6 week training for becoming a service technician
Thank you very much Omar. There are around 40 articles on there too at patreon.com/acservicetech On that video I just don't think I had it wired. Good observation!
Great video ty
Thanks Jonathan!
Hi this is Blaze from SoCal again. You are up early. I have a question. I do all commercial. I also only carry Ventstar 2800's thermostats on my truck. Recently I had a problem with a stat. When I got a call for heat the reversing valve did not de energize. I was working on a Trane Voyager. I jumped across the test pins and the unit went through all operations. The units okay. I removed the thermostat from the wires and jumped out the unit there apart from the stat. The unit heated and cooled. Bad stat? I replaced the thermostat with the same result. I know my low voltage wire is okay but I still checked it out. I then replaced my low voltage wire at the unit with new and attached another T2800 to it with the same result. I'm pulling my hair out by now. Anyways I went to my vendors and picked up a Honeywell 6000 and am going to try again tomorrow. Any suggestions? Thank you again for a great video!
Do you have the reversing valve switched from B to O? R powers to B in cooling mode and R powers to O in heat mode. These are for the reversing valve depending on if the unit powers the reversing valve in heat or cooling. When you said you tested the system with the tstat wires disconnected from the tstat, I am assuming you already wire nutted the correct wires together to get heat right? thanks Blaze! Yeah in reference to the time you saw the video was uploaded at, that seems to be the only tim e to try to get them done. The kids go to sleep at 8 and I work on a video from 4-5 hours to get it done edited, and all the rest, ha ha thanks
acservicetech Thank you again for the great videos. Ahh to be young again. I'm in bed by 9 at the latest and then up at 2:45 the next morning. Regarding the thermostat issue. Both of the T 2800's that I used would not de energize the coil when I went to the heating mode. I installed a Honeywell 6000 and it controlled my unit correctly. I took the 2800's back to SIGLER for warranty. Thank you for the reply. Merry Christmas to you and your family!
Thanks great video
Thanks drummer!
that is an awesome tutorial there partner! how can I subscribe to the channel you talk about? I want to learn more advanced troubleshooting and other task that are not on the tube?????
So I have about 20 community level posts there and more to come but it is also for those who want to ask more questions and a way for those who choose to support the channel here. Check out the video I made to explain it at the top of the screen at Patreon.com/acservicetech Also so you know, I am in the process of writing a book. Thanks as always!
very interesting 😎
Thanks Hector!
So the five minute delay is programmed inside the thermostat or part of the air handler board?
Inside the thermostat and also sometimes inside the outdoor heat pump board, thanks
The heat on the thermostat will not turn on without me turning it off then on again or going one degree below room temperature then back above room temperature. Why is that ? I can put the temperature to 76 but it won’t turn on only if I do those steps . It’s on heat and auto but will not turn on unless I do those steps. It’s a new thermostat
thanks
I had a new HVAC system installed last year and a honeywell stat that has 4 wire running to it.(no C wire). The system when in A/C mode will set there and run until I turn the stat up, but I have to turn it up 3 or 4 degrees or the temperature reading will jump a degree or 2 to match where I set it to. I know sounds crazy. It will also jump down and match within a degree or 2. SO... first I called honeywell thinking this must be a stat issue. They had me test the voltage readings of the 4 wires running to the stat. The 24v red was fine but one of the wires read lower like 9v and seemed to vary. Honeywell blamed the HVAC system as the problem. So I called the HVAC tech out and after thinking it was the wires running to the stat he checking the voltage readings at the unit with the stat wires removed, he got the same readings ( one circuit was low and varied) eliminating the wires to the stat as the issue. He then said it was an ECM module/motor.He did a warranty replacement of the ECM and said it's fixed. For some reason this issue takes a few hours before it acts up. Then the longer it runs the worse it gets. He finished the warranty repair and said even though the voltage is still low in one circuit the system was working fine, but the next day it did the same thing. I replaced the Honeywell stat again and it does the same thing also. Any ideas what I should do?
do you receive pay pal?????
I am actually working on it. Check out Patreon.com/acservicetech, thanks Jimbola77!
Hey jimbola77, I finally go the paypal account set up. They had a hard time linking to the account. Anyway it is now set up for anyone that wants to contribute to the ongoing work of the channel instead of through Patreon- www.paypal.me/acservicetech - Thanks for your consideration either way and as always, let me know if you have any HVACR questions, thanks
Useful video like +++
Thanks Elektronik!
Why can you DETECT VOLTAGE across a load that is energized from THERMOSTATS, but not from a SWITCH when the load is energized?
I know this is super late, just in case someone else is having this question.
When you are taking voltage across two points in a circuit, you are reading the difference between the two point. The C terminal is a straight connection to the C side of the transformer. The R side of the transformer is what is being switched by the thermostat to the W, Y, and G terminals to make the various calls. We see voltage because R and C are 27 volts RMS apart from each other.
If you were to read from R to Y, and there is a call for cooling, then you would read 0 volts because the voltage is the same across those two points.
Yeah mine's not wired like that at all
"...what this means is that ores coming into the thermostat..."
ores? WUT
oars?
Even the transcript generator is confused.
You did not show how to check if the thermostat has a battery
Comon and r24v
I have no common wire
Then you wont be able to take any voltage readings at the tstat but you can at the furnace or air handler, thanks
All techs should explain 'what setting' the volt meter should be set at because we might, and I do have a different one than you
When speaking pleas SAY ac voltage. when appropriate
Why ??
I have no C
B I’m
great video thanks!
Thanks Alex!