Air Con HVAC Controller Board Repair : How To Diagnose Faults
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- Опубликовано: 8 фев 2025
- A customer asked me to look at a PCB from a split air con system. It generates an error code, but I don't know if the fault is on this PCB from the outdoor unit, on the indoor unit control board or something external to the controllers. In this video I take a look at how the comms between the two PCBs works.
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Thank you
Richard
Hi Richard, I've been watching your videos for a few years and am frequently entertained as well as educated. Thanks for sharing your wealth of knowledge.
On the specific board: you are looking at the condenser control board for a variable speed compressor control. Not only does it control the speed of the condenser fan but it also controls the speed of the compressor motor itself. The Motor is an ECM-type motor. Basically it is a three phase motor with permanent magnets in the rotor instead of rotor windings. This makes it function like a DC motor with three windings. The U, V and W leads are the outputs of the large chip under the heatsink. The microcontroller generates a PWM signal to the chip inputs and the chip modulates the DC supply into high power output for the three compressor windings. The compressor speed is controlled by the microcontroller varying the duty cycle of the outputs to the compressor motor. Basically this operates similar to a three phase VFD except for the output being PWM modulated DC. Hope this helps fill in some of the gaps and explain the "three phase like" appearance of the board labels.
Regards, Wolf
hey rich, the UVW thing ist to understand like that. each letter is the name of one winding, the number is the side of that winding (3phase motor/compressor). so U1 phase1, V1 Phase2 W1 phase3. for star connection, the other sides will connect together (usually inside of the compressor), the "new" name for them is U2 V2 W2. i'm pretty sure you know that already as XYZ (the old name for exactly the same thing).
As this circuit has basically the same output stage like an 3 channel half bridge amplifier, you should check the output devices. pay attention that this is a single module which contains all stages and sometimes even the control logic needed for it. only way to analyze these will be the datasheet. usually they have one high voltage DC input and the matching ground, a smaller voltage for driving the bridges 3 pairs +-15volts DC and separate 5 volts for logic with separate logic ground. these devices usually fail because of overcurrent and overheating, caused by compressor overload conditions. proper maintanance can prevent that (cleaning the fan and the condenser). hope this helps.
Well done Julie !! Great Job. that's how to prove an OpTo.
Been looking for a video that clearly shows how to test relays in circuit for control boards. Thanks m8!
I've shown how to test relays in circuit during repairs but not on a specific video, I'll do that soon
U V W generally relates to three phase power / motor.
32:26 Most test points on modern equipment are not service test points, they are used to test the PCB during manufacture for continuity in the traces.
Det also suggested the manufacturer had a bed of nails (pogo pins) which they place the PCB against to do some sort of QC/Functionality test. Sounds like a similar idea to yours
@@LearnElectronicsRepairThey are often used for programming as well as testing. The manufacturer of the Camera control units for drain cameras I work on use a bed of nails for QC and Programming firmware anyway.
Another great video along with your lovely assistant! Cheers
26:29 A lot of IPM failures occur. That is in the time stamped video in the top left. An IPM module generally contains power transistors (like IGBTs), a dedicated driver circuit to control the transistors, and various protection circuits for overcurrent, overvoltage, and overheating situations.
To test IGBT set your meter on Mega ohms. Place one lead on the P+ terminal, at the capacitor.
Place the other lead on:
U and record your reading
V and record your reading
W and record your reading
Take the lead off of the P+ terminal and put it on the N- terminal.
Place the other lead on:
U and record your reading
V and record your reading
W and record your reading
Are these readings close and consistent? If so, the IPM checks out; if not, replace the IPM.
@@USA-GreedyMenOfNoIntegrity Thanks 🙂
@USA-GreedyMenOfNoIntegrity Happy to see you hear and explain this stuff... well I remember you from the comments you made on my video... Great and rich also did a great job..
Communication error between indoor and outdoor maybe caused by optoisolators on both inside and outside boards because they are used for communication signals
HVAC Tech here and really appreciate you covering these. They are getting much more popular in the USA. A lot cheaper for DIYers and the central hvac unit costs have increased 100% in the last 4 years.
Midea "AG ECO" service manual looks like it might be helpful
4:09 The Wire terminal is for the compressor, not the Reactor.
Slip an old credit card down the side, then lever on that with the screwdriver. At least then you don't accidentally gouge any tracks underneath.
On the opto that you tested out of circuit I noticed what I suspect is an anomaly that you missed - out of circuit the voltage indicated when activated was 6 plus volts, in circuit the voltage drop indicated was 4 plus volts. You were never going to see the opto work in circuit, as it was masked by the rest of the circuit. I suspect that there is a fault in that circuit somewhere, as the circuit likely wouldn't sense any change whether the opto was activated or not...
Thanks Will it would seem this needs a little more close attention. This is exactly the sort of suggestion I was looking for
Little information is the hallmark of the trades and their corporate overlords!
LOL You used a neato tweezer type solder iron (nifty) but not tweezer style DMM probes for the OPTO. Maybe Julies' video contract stipulates more speaking roles? :P
I find using IPA alcohol very effective at loosening glues.
Especially 'hot glue'
This is the Midea Control Board, Used in Many Air Conditioning Brands.....
Of course you now a lot more about these things...I watch your videos on your channel forever tech. All the best!
I would like to know more about the error code and the make and model of the unit it runs.
Sometimes glue is used for anti vibration/dampening.
As far as I can see it connects to 230V single phase and the compressor motor is 3 phase (UVW). I think the board is a variable speed controller
WUV three phase motor for the compressor
Yes, correct. To 3ph dc compressor. Pulsed dc at varying frequencies/current controls compressor speed typically between 25-100% rpm.
And sometimes XYZ. I did get there in the video after a little while, I leave this stuff in so people can follow my thought process as I work stuff out.
You have to check optoisolators on both boards there should be some voltages to be measured as the two boards are speaking to each other
@@mda420 correct
You oldtimers should also remember RST then.
Crow bar or tire iron?
I sometimes find it hard to follow you as you understand what you are looking at but us noobies don't, same with your understanding of the circuit. I'm sure that with enough watching I may come to understand like you, but in the meantime perhaps a bit more clarity in why you feel a certain resistance is ok. thanks,
@robertclarke2365 That is the perrenial problem, where to pitch the level of the video when there are so many peple watching it who are at different levels. So I often vary the level between videos and some are more suited to beginners than others. Did you watch this one I published a few days? ruclips.net/video/NmwSjEGS3R8/видео.html It's a good place to start if you are wondering where to begin with this sort of repair work. There will be a part 2 of that coming in the next few days and in that one I cover resistors and when, where and why they are likely to fail.
Anything you would like me to clarify or explain more in this video just ask me in comments with a time stamp of the section of the video. Or ask on the live stream every second sunday if you can make it at 5pm UK time. Sometimes I read comments to my repair videos where viewers are struggling with certain topics and then I will make a follow up video if I think this is an area that a lot of people will benefit from a more detailed explanation. So feel free to ask away, I will try to answer and in fact this also gives me a good source of ideas for other videos 🙂.
Robert, I'm not sure if you know but Rich does great videos on "How to ..." and a great series on "All you need to know, series...." also many other teaching videos that are all very addictive if you are really interested in learning about Electronics repair.
I have found that Rich is one of, if not the best educator on RUclips and goes way out of his way with in depth explanations.
I knew almost nothing about electronics repair around 12 months ago and Rich's videos were one of the first videos I came across. Now I'm repairing electronics but still learning, obviously and I still watch Rich's videos over and over again, each time learning something new.
Seriously, take some time and go through Rich's vast catalogue and I promise you will learn so much in no time.
I'm not a very smart guy, so if I can do it, anyone can do it, you just need the passion to learn.
Cheers mate and good luck!
@@darrenbird2526 Wow. Thank you. And to be honest I'm stil learning too... that never stops
All the ones that I have worked on in the USA have a second board in the outside unit
This is the outdoor unit board
My experience from getting PCb’s like this… It is almost never this specific PCB that is faulty, but something like thelarge BLDC fan sitting downstream, or in another case the wiring. It always feel weird telling the guy bringing the PCB that everything looks fine, aafter ou went through all sorts of tricks trying to stimulate the inputs, and measuring the outputs, hoping you have it all right, before you tell the customer the PCB you received is ok, but the fault is in another part if the system…
This could well be the case. Ialso know the air con tech involved with the particulay job so between all of us maybe we can figure it out and all learn something. Thank you
Your multi meter was quiet today, im getting old and deaf but it was a lot quieter than usual, unless im going nuts :)
Are we certain the error code is EL rather than EC (refrigerant leakage sensor) ? (Seven segment display with a missing element?)
That could be correct, didn't think about it. The on site tech did say the refrigerant pressure was OK but it is very good to think outside the box
sure that part was a plug in module, so it could be changed out for a replacement module
That’s pretty much all of us HVAC techs do in the USA. Swap them out. $$$$ I’m going to learn how to repair them.
Yeah it could if you can get one and if it is not prohibitively expensive.But having said that the purpose of this channel is to learn to repair stuff not throw it away and get another one.
@@USA-GreedyMenOfNoIntegrity And that is something I am trying to teach, and learn at the same time. So keep following along with me and feel free to jump in with any suggestions or ideas. There appears to be too much fog and mystery surrounding these PCBs and as far as I can see they are not so complicated. Either no one knows anything much about these boards or some people do but are not telling anyone else. So far I find them fairly easy to fix if they are dead or blown up (did you see the one with the fried lizard? ruclips.net/video/b8vHr96tBoM/видео.html that one worked fine after my repair) 🙂 It's this Error code F4 F-whatever etc which is proving more of a challenge but let's see how far we can get. I expect these boards are pretty much the same once you get your head around the design and architecture of the board, a bit like ATX PSU or Class D Amps, once you figure out how they work ,because they are all basically doing the same thing, then you can repair most of them regardless of the manufacturer or model. I have another air con board to look at next week, different make similar error, maybe that will shed more light
Heya, yes it's to bad that there is so less info and shematics on these PCB board's I have the same problem with my inverter
This is Midea pcb.
UVW on a connector says three phase to me.
Chisel and 10lb lump hammer works every time. Only problem with this method is putting back together can be very challenging if not impossible. So should only be used by professionals who are good at hiding from the customers.
In the service manual I think I saw an error state red-blinking, green-off and a description - eprom error…
Looks like green-on red-blinking…so maybe not
Too E1 error i found the relay on pcb from indoor unit.
Heah try hot air to soften the plastic.
Hi Richard, just had a quick look about on youtube. Found a video on a similar unit, where EL01 code error was a communication error between the inside and outside units. Here is another video on testing the communication ruclips.net/video/kNak_SM4CAw/видео.html
Thanks I'll check that
Have u activated auto translation for video titles ? if so, from my sight, this makes absolutely no sense. as german, if i see a videotitle in german, i assume, it's a german video. if i'm looking english videos, than i can understand english, and hopefully also read an english video title. And many times, the translation is this bad, u have to look in the video to understand what it means. But we as German are now lucky, the last time we get german videos, with an Ai voiceover in english, this is also absolute BS. YT PLS STOP THIS BS!
Dave from EEvBlog had 2 separate videos about the AI translation which was enabled in his account. Silly RUclips sees that you are say in Germany so it changed the audio to their poorly translated German AI version automatically.
No I didn't activate it, this is something RUclips are doing as a new feature and I got selected as one of channels who are testing the new features. Regards the AI voice feature most of those who commented say they like this feature. I didn't know about the auto translation on the title text though. I've asked my RUclips partner manager about this.
@@GregM As a german, i had german Videos translated to AI english ^^ but this u can change on the gear.
JE Me Demande qui est le Type qui traduit en français mai il est Nul a Chier!!!!ou alors c'est un Robot généré pars L'IA!!!!!EN Plus tout sa pour ne rien Réparer c'est trop Nul!!!!!!!