In my last post I mentioned that — later this morning I am going out to meet a tech at a job site where the company has replaced 3 of the same control boards in the first 7 months since the unit was installed — what do you think the odds of that happening are?
Well, believe it or not — it was true — HOWEVER….! Yes, they really have lost 3 control boards in 7 months. All of the board failures were the same thing, the board would not turn on the main blower contactor so they had limit trips in winter and lock-outs on low pressure in cooling. So every time they found this problem, they replaced the board. BUT the real problem here is they never found the cause of the board failing — they just kept replacing it because it was bad!
What we found on site was that the main blower contactor, which is what the board should energize, would “buzz” and draw high amps about every second or third try. So when the contactor would try to pull in, it caused the small pilot relay on the board to “chatter” and burn up the contacts inside the pilot relay thus rendering the board “bad”. They thought the contactor chattering was because the board was bad and never diagnosed the contactor being bad. They did the proper diagnosis to determine that the board was bad. I can’t take that away from them but you would think that after the second one failed they might have looked a bit further and surely, after the 3rd one failed — really looked. But that is why they had me on site because they thought we were having a “run of bad boards” :>)!
You would think that they would have at least change BOTH parts since the contactor was chattering which had arced the contacts and had them burnt a bit (and gotten lucky and solved the original problem) but they didn’t.
All of this comes down to again is getting techs to look at the whole picture and make a proper diagnosis. I did use this site visit as a teaching experience for the tech and, hopefully, the tech learned something and won’t just keep replacing parts without finding out why they failed in the first place.
It all comes down to this – making use of flash code and doing a complete diagnostic to make sure the problem is completely addressed. Even here, the flash code was limit tripped or low pressure — both usually related to air flow. Yes, they found the blower not running. Yes, they found the output from the board not present. No — they did not see why the boards kept failing and just kept changing them. I’ll give them the first one– but after the second or third, a “red flag” should have gone up and it should have been determined why the boards were failing. It all comes down to common sense troubleshooting.