Good advise here, chewing up contactors "usually" means chattering contacts, for whatever reason.
FWIW
As a side note..
Was at a school a couple of yeas back and they had a system that was doing this and blowing boards.
Then it went onto premature rusting. This was to the point of having to replace the C.U. under warranty because of the rust!
This was a M.H. and they found "amps" on the ground rod. Fixed that and everything went back to normal.
Life is too short, Behappy!
TFMM
Watched defrost cycle and it was beautiful
I rather do nothing and be happy than to do something and not be happy
I'm just guessing at remote scenarios...and not familiar with York single stage, let alone, 2 stage systems.
Are you leaning towards a heat cycle specific / contactor chatter issue?
Do W1 and W2 energize separate heater controls? Have you tried getting stage 2 compressor (Y2), and stage 2 aux (W1 & W2) energized, and then maybe, throw in a defrost to boot?
What about the heat cycle pressures and possible limit switch glitch?
Even if you have two switches in series, you can still put tattle tales in parallel with each of those two switches to see which one opens, if that's something that you think will help you with your diagnostic approach.
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2 Tim 3:16-17
RSES CMS, HVAC Electrical Specialist
Member, IAEI
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Just an update, I haven't been back to the job since I put Supco oil in the system. The stuck reversing valve must have been the problem. I still don't understand how a reversing valve sticking would burn contactors up like it was doing.
I rather do nothing and be happy than to do something and not be happy
I rather do nothing and be happy than to do something and not be happy
Does it have a " cfmcb" board?
That bad brd was the cause of our mysterious chattering
Just an update. The supco oil did the trick. I haven't been to this job since I put the oil in it. Crazy how it was eating contactors through
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I rather do nothing and be happy than to do something and not be happy
I had a lennox do this. The stuck reversing valve eventually caused a low pressure switch to open but would immediately close and cause a hideous short cycle. Not a subtle failure as it sounds like it's being beat to death with a metal broomstick. Some of the oem pressure switches are crap. Especially the ones that look like a $3 flame roll out switch. FYI the RV would switch fine in warmer temps but would stick overnight when it got colder.
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I rather do nothing and be happy than to do something and not be happy