From Problem to Solution: HVAC Contactor Troubleshooting and Replacement
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- Опубликовано: 10 фев 2025
- In this video I explain step by step how to troubleshoot and replace your HVAC contactor. It's a very easy job to figure out if that's your problem or not and it's just as easy to replace it. I also give some tips as to what else could be wrong when you have a unit that won't come on.
Thank you sir. It has been tight with money since the wife stopped working do to illnesses. This was a huge savings.
You're welcome! So glad I could help... 😊
You my friend just saved me 100s of dollars. Although it took me several hours of troubleshooting, once I found you video I knew it was a high probability that this was my problem and I was right. Thanks for saving homeowners from having to call a technician for potentially small and easy fixes.
You are welcome! I'm so glad to have helped... Yes for a $15 dollar part the HVAC companies will charge $150 plus. It's understandable, but I like to save $$ whenever possible... 😊
What was happening to your ac unit which led you to changing this? I’ve changed the cap on my unit but now the ac unit works until about noon then shuts off and sometimes comes back around 6pm.
@@naelonachermann4613 HI. In my particular case I changed it out for preventative maintenance ... The best way to tell if your contactor is causing the issue is to check your low voltage if it's not already pulled in when the thermostat is calling for AC/ heat. Sometimes there's a plastic plate covering up the button so you can't tell. If it's pulled in you've got low voltage.. (Should be about 26 VAC). If it's pulled in check the output of the contactor and see if you've got 240VAC. Don't attempt this if you're not comfortable working with live voltage. If you've got 240 vac coming out and your unit isn't running then something else is wrong.
Thanks, Rudy. You're making this easy for us.
You're welcome! Thanks for the feedback... 😀
Good video. It was helpful explaining the single vs dial pole. I’ll be replacing mine along with a new Capacitor in a few days.
Excellent! Thank you for the feedback... 😀
Most helpful! Thank you. My capacitors were over heating.
That's a common problem. I'm glad the video helped.
Very good video! Well explained and clear. Thank you.
TYSM! 😀
Nice video. I am not a prof in this area. But I just installed a new contactor, the old was rusted and broken, but the plunger did not pull in when I turned on the thermostat. I am sure I installed correctly because quite simple, took pictures, and when manually pushed in the fan/compressor run. It seems I can only see the reading of 26v on my volt meter of the control wires from the inside transformer only when the plunger get sucked in otherwise 0. My question is how do you test if the control wires actually get 24v without connect to a contactor? Thanks
HI, if you have 26vac between the blue or "C" wire (Could be black) and the red wire (I'm assuming you're working on a heat pump) then your transformer in the air handler is in good shape. When the T-stat is calling for heat or ac the yellow wire should be energized coming into the unit. This yellow wire should be the one to energize the contractor. Depending on what unit you have, the orange reversing valve may or may not be energized. Most of the time it's de-energized in heat mode. If you have nothing on yellow coming into the unit, I'd check out the t-stat... Between yellow and common... Hope that helps.
Great Video!
Thanks for the great feedback... 😊
Great video, you got me cool again. You the man! Thanks for posting.
That's awesome! So glad I could help...
Thank you so much your video , help me learned new things
You're welcome! So glad to help.. 😊
Can you explain what the symptoms were before replacing the contactor? Was the outside unit completely dead or could you hear the compressor running but no fan spinning? Thanks.
HI, in this particular case I replaced it for preventative maintenance... Usually when the contactor goes bad you might have a little humming noise and the unit isn't running... It'll affect the whole unit compressor and fan. The best bet is only if you're comfortable with working with electric take a volt meter and see if you've got your 240 VAC coming in from the house but it's not on the output of the contactor. If you see this, make sure you have the low voltage 24VAC on the coil of the contactor.. If it's not there then it's probably not the contactor but the problem is somewhere else of which are many possibilities. Hope that helps.
@@TheHomeImprovementChannel Thank you for the tips. That helped. The 24VAC was at the coil of the contactor and it pulled in the contactor contacts which turned on the compressor and fan. The problem I am having is the unit is not getting out of defrost mode. It's possible the compressor coils are not getting hot enough (80 degrees) to open that little defrost sensor clamped on the compressor coil. I'm not an HVAC guy. Just a homeowner learning what I can on RUclips. Thanks for your channel!
Yes it could be ... I've also seen the circuit board inside the outdoor unit fail.. That does control the defrost as well... If you search RUclips for possibilities on defrost problems, you should be able to find a video that someone did outlining all the possibilities. That board will send out a signal to the reversing valve to switch it into ac mode which sounds wrong, but it actually is able to heat up the coils that way... One other thing, it's a long shot but if you're stuck in defrost there's a possibility the reversing valve could be the culprit. @@georgeterbush2976
@@TheHomeImprovementChannel Thanks again for the suggestions. It was warmer yesterday so I turned the heat pump on and it was in defrost mode for a few minutes, then Whosh, the reverse valve energized and the fan started spinning again in normal heating mode! I'll keep an eye on it. Thank you.
Oh cool! If it turns out to be an intermittent problem, I ran into that once and it was a major pain! It turned out to be the defrost board... @@georgeterbush2976
This is super helpful just the thing i needed
That's awesome! SO glad to help... 😊
Hi- I am having trouble with condenser turning on and off within multiple times after start up.
>I replaced contactor- didnt work- got 24v at contactor then 11.4v then volts moves all over.
>I replaced transformer- same thing.
I just watched your video- i wonder if timer relay could be the issue? Not sure if power comes from or to relay? I have timer relay + 1 other one. I appreciate any help.....Unit is rheem/2003
HI Rick.... I would want to know if your high voltage is making it through the contactor... Or is the low voltage cutting out.. Somehow you need to monitor it when you are seeing the problem happening. If the low voltage is cutting out (which I suspect it is) and you've already replaced the transformer in the air handler unit.. I would suspect the thermostat itself or the wire going between the air handler and the condenser... The yellow wire coming from the thermostat is the one calling for AC.... if the power on the yellow wire is cutting out, then that's probably a thermostat. I've also seen loose connections under wire nuts...
What contractor did you replace that with I've been looking all over for a contractor I can't find one with the exact numbers and mine is just like the one you replaced
The exact numbers may not be super important. The voltage is usually 24 volts and you'll want one that's the same amperage. Depending how big the unit is... Also if the original was a single pole or double pole. The one in the video I just got from Amazon.. Hope that helps.
I’m in the same boat as you @nitadavenport3964 I managed to find one pretty dang close from Walmart but the LSA is 180 not 150
Hi, I have an old A/C unit and the wire from the capacitor to the contactor keeps burning up. I’m gonna replace both the capacitor and contactor but i’m having trouble matching the RES with any newer model contactors. The one on mine says 30 RES but newer ones say 35 RES that match all the other specs on contactor. I did read something that said RES doesn’t matter on a A/C contactor but wanted to get a second opinion?
HI... In my opinion if your RES is the same or higher than the original that would be fine. The unit is still running through a circuit breaker that is probably 30 amps in many cases... Of course this is just my opinion. 😊. BTW if those wires keep burning up there might be some extra resistance somewhere. Like a bad connection. Yes it's possible the contacts in the contactor could be causing that. High resistance always will cause more heat.
Thank you! I appreciate the help! Great channel by the way!
@@matthewjones950 You're welcome!
I have ca Gooodman rooftop AC unit. The unit was working fine until yesterday. One of the motor bearings froze and the motor wouldn't turn. I repaired the motor, and now the contactor won't engage. If I manually push the contactor everything turns on and the unit works fine. Any ideas??
Did you check if you're getting the low voltage to the coil of the contactor? Should be about 26VAC... If not there could be several reasons for that anywhere from the thermostat to water in the condensate pan to a control wire might have come off somewhere while you were working on the motor...
@@TheHomeImprovementChannel Thank You for responding so quickly. I check so many things yesterday. If I have voltage at the contactor than it would be a bad contactor, yes? If I don't than, something on the board? I don't know how long the unit was running with a froze motor the current draw had to go up while the motor was stuck. I'll check the voltage when I go back later this morning. Could the escessive draw cuase the contactor to go bad? There is no float switch as the unit is on the roof. Like I said if I manually engage the contactor the unit works great. I'm thinking it has to be something simple, but who knows, I would really appreciate any insight you may be able to give me. Thanks Again!!
@@TheHomeImprovementChannel Also is the motor and condenser on a time delay?
@@jimm9577 HI again... of course seeing it would help a lot! If you're able to push the button on the contactor then the load from the motor probably didn't cause the problem since the coils are separate. You need to know if you have low voltage before you can move on... Yes if you do have low voltage and it's not engaging then it's bad... I wouldn't suspect the board at first. Usually that board has a fan relay and some defrost stuff if you're using a heat pump.. Of Course in a self contained it could be different, but I think it works basically the same way... The yellow wire from the thermostat line coming from the thermostat is usually the one calling for AC unless someone wired it differently. Turn on the thermostat and see if 1... You have your 26VAC on the red wire (should be all the time power) and then if your thermostat is saying ac should be on check the yellow wire where it comes into the unit.... Yes there's a time delay. Usually about 5 minutes.
@@TheHomeImprovementChannel While I was checking the voltage on the board at the terminal for the trigger wire to the contactor, I accidently hit the terminal for the reverse signal (for a micro second) and the contactor engaged, the fan started working and the compressor kicked on. Double Dumb Luck!!! It's been working ever since.
Nice video. Ta!
TYSM! I really appreciate it... 😊
Where did you buy the contactor? Our local HVAC wholesale does not sell to the public.
Yes they've got it locked up that way.... Fortunately you can get a lot of parts like that from online retailers pretty easily. I got this one from Amazon, but there's a number of retailers that sell HVAC parts. Refrigerant does seem to be a bit harder to get even if you have an EPA card...
My daughters LG air conditioner, after being cleaned by a technician recently, started to work differently after he left, e.g. when I turned on the inside unit, the fan blows at full capacity and then the inside unit shuts down. The outside motor (compressor) doesn't kick in at all when this is happening, and then the inside unit that is blowing the fan at full speed shuts off within a minute. I rang the technician and he said that he was willing to come back to have a look at it and of course take my left arm for the problem he caused in my opinion, because it was working fine before he pulled it apart to clean it, so I told him to FO in the nicest possible way. I am not in anyway a technical kind of guy, but I think I can change the capacitor by myself, if that is what it is. I would appreciate any assistance that anyone reading this can provide me with, e.g. do you think it is anything else apart from the capacitor. The outside motor (compressor) kicks in after about half a dozen attempts at turning it on and off, when the inside unit was blowing air at full speed, so it sounds to me like it is the capacitor, as that is what gives the compressor that extra kick from videos that I have seen. Appreciate all assistance in advance.
HI, without seeing it there's no way to really know what's going on. But if it was working before he came, he probably knocked a wire loose somewhere. To me it doesn't sound like a capacitor. I probably would have let him come back, especially if he caused the problem..
@@TheHomeImprovementChannel Thanks for getting back to me, yeh he was pretty rough with his work, and I did tell him to come back to sort it, but he said he would have to charge, that's when I said, yeh nah, your toast, we have 7 air conditioners here and he won't be touching any again since he's attitude sucks, especially when he lives up the road. I will open up the inside unit and see if there are any loose wires and go from there.
Interesting.
TYSM!
Just to be clear you were referencing the 240v at the contractor but you said to shut off all the power in the beginning. ???
Yes I always recommend shutting off the power before beginning a project because I don't know who's comfortable working with power and who's not... if that makes sense. However there are times that you have to turn the power back on to test stuff and that's where someone not comfortable shouldn't attempt to do that...
Where is the 27v transformer? I get that issue. 240 on connector, no 27v. If i push manually everything works. Nest inside house says system is running happy. Where do i find the transformer plus a fix?
HI! It's really called a 24V transformer even though it's more like 26+... Those are located inside your air handler somewhere close to where all the power hookups are. If you're not comfortable removing the covers on your air handler and working with live electric, I absolutely don't recommend you do this job yourself...
Thank you. I've traced down the cables to inside my house and then to the furnace board where one small hidden cable was broken into 2 pieces. It took me hours to find because it was connected but almost inside the plastic cape it was loose. Fixed and saved at least 200 bucks. Thanks
@@jhguygih That's so awesome! That's a good find and you probably saved more than that!.. Good job.
@@TheHomeImprovementChannel I have the same problem, no 24VDC on the contactor coil, I already change Thermostat, Transformer, and still not 24VDC signal, any other recommendations.??
@@jhcruzOficial01 Check the red wire coming into the heat pump to verify you have 24 volts coming from the transformer and thermostat... If so, pull off your thermostat and jump 24 volts from the red wire to the yellow wire. I would also disconnect the yellow wire from inside the heat pump so you don't risk damage. See if your 24 volts is making it all the way through. You might have a bad wire. Also make sure your blue or black wire which-ever one is common on your unit... Usually it's the blue wire on the thermostat wire.. make sure that one is making good contact as well...
Could a bad contactor keep blowing a fuse at the disconnect?
HI... It's doubtful. The best thing to do is isolate things from the circuit until the fuse stops blowing. For example if you suspect the contactor you can disconnect the output of it leaving the low voltage connected so it'll engage. If the fuse stops blowing you'll have to move on to the next thing. I would find out which wires are coming from the compressor and disconnect those and see if it's coming from that. Obviously if you're not comfortable working around electrical things then don't try it, but if you are, that would be my strategy..
❤
I found this video, but literally the information I need is: I don't have 24vdc in the contactor coil, the transformer is new, new thermostat, what is the other possibility? My problem is the absence of 24vdc in the contactor, why?
I think I just answered your query on the other comment...
It’s 24 VAC not DC.
Make sure you set your multimeter correctly
@@neilkurzman4907 HI, Did I say DC? If I did it wasn't intentional. I know it's AC.. 😊
@@TheHomeImprovementChannel
No, the post you responded to indicated 24 VDC
I just wanted to know it because if somebody set their meter to DC it might be zero when there was actually voltage there, as you well know
@@neilkurzman4907 Oh yes... I didn't catch that they wrote DC... Thanks for the correction. 😊
My button stay down for about an hour and kicks back up, any reason why?
Im assuming it's not as simple as the unit cycling on/ off?
I used to work everything hot. I replaced all of the light switches and outlets in my parent’s house energized. It was more fun that way. I didn’t have any problems. I used to work on everything hot at the power company to keep everything energized too. I just got used to it. It prevents any mistakes if I’m wrong about something being de energized too. I treat everything as being hot. I don’t recommend it for normal people though.
Oh yea, i've done that too.... But it's like you said, I can't recommend it for someone else.. 😎😎
Ridiculous statement.
Same here until I shocked myself. Now I take the extra 2 minutes to kill power and test everything. Much less stressful
You brave enough to try that on 460 volt 3 phase? 😅
WOW very impressive Mr. Electrical man!
My fan dont come on on auto, but on if put fan on on.
Without being able to see it, i'd only be guessing.
My outdoor Fan comes on in cooling, but not heating😥 the blower works on heating but the vents push our cool air when they temp is set to 78
HI! The outdoor condenser motor doesn't know the difference between heat and cool. Are you sure it's working in cooling? It's winter and maybe it has quit since AC season....
If You Donot Get 24v,
1. Replace Breaker Or
Wire Is Shorted.
2. If You Donot Get Continuity
In Contactor Means Bad Contactor.
Amén.
Thank u!
I currently have 24v coming out of the house and going into the circuit board but no 24v at the contactor
HI BingBong..... You won't have 24V at the contactor unless your thermostat is calling for AC/ Heat. Turn on your thermostat and let it call for heat or ac and see if anything shows up on the contactor...
@@TheHomeImprovementChannel heat is turned on at the thermostat and still not getting 24v at the contactor
You say the first step is to turn off the power. Then you say it's a good idea to check the power going into the contactor. So I guess that is really the first step. Do you agree?
HI... No I don't actually. When someone is removing the electrical cover if you're not used to it, there's a chance you could short the metal cover onto the exposed leads coming into the contactor. A small chance, but nevertheless a chance... 😊
@@TheHomeImprovementChannel Good answer. I agree. Thanks.
Can I just set the thermostat off if I want to troubleshoot
@@Jaylenn. HI... Depends on what you are troubleshooting... 😊
@@Jaylenn.it’s 24v going to the contactor from your thermostat . You need to shut the power to everything so nothing happens
my connectors are rusty and the ground 1 just pulled off,maybe the prblem?problem?? any thoughts
HI, yes if your wires are pulling loose that's a bad sign, but without seeing it I can't be sure of anything. If you have a volt meter, try to see if you have continuity through the contactor. I doubt the ground pulling off would cause the unit to not work... (But I would still fix it)
Yup problem solved thank you just rest the contactor and it kicked right on and also there was a rat nest 🪹 😂
Oh yea they'll build a nest in there. Could be mice, they like doing stuff like that. Glad you got it going again... 😊