ReplyI had one last week that would work fine If I jiggled the molex but once It shut down it would keep throwing a ps switch code eventhough inducer never ran, then jiggle again and it would run, new board fixed it.
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Had a Coleman doing this exact same thing about a month ago, bout kicked my butt, finally after 1.5 hrs of troubleshooting, I noticed were the installers use the on board transformer to also power the zoning, I pulled the power leads off the transformer to the zoning box and and it worked like brand new. I don't see how the system lasted 2 years before it finally started acting up wired this way, maybe one of the zoning motors started drawing a little more or was going bad, and stressed the 40va transformer more. I stuck a new 80va on there for the zoning and have not heard a peep back.
__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
Professional Member*
I had one last week that would work fine If I jiggled the molex but once It shut down it would keep throwing a ps switch code eventhough inducer never ran, then jiggle again and it would run, new board fixed it.
Professional Member*
Originally Posted by evilsanta
If this unit is "around" 5 years old, the board should still be in warranty, and the HO should not be buying any boards period. Most mfg. have a 6 month install grace period. If it were a Ruud I could warranty the board all the way to 5.5 years, and would if the customer was nice to me.
__________________________________________________ _______________________
“Experience is a hard teacher because she gives the test first, the lesson afterwards" ~ Vernon Law
"It's what you learn after you know it all that counts." ~ John Wooden
"When the teachers become unteachable we're all in trouble" ~ Mr. Bill
"Remember "Pro" is only a name, it's not always a mindset determined to do everything correctly" ~ Mr. Bill
Regular Guest
Went back this morning and began trouble shooting at ground zero. Found that the pressure was acting up. Started the furnace and the problem began immediately. Let the inducer run for a sec and jumped the pressure switch and it ran fine. I tested it time and time again with and with out the jumper and had the same result 20 out of 20 times. Changed the pressure switch and tube. The board never coded the entire time with the failure. Thanks for the incite. To add Mr. Bill the customer never once purchased any parts, there was another company involved prior who I work for. The unit was out of warranty besides the heat exchanger.
Professional Member
I had GOODMAN call same thng ended up being bad pressure switch
Professional Member*
I've known pressure switches to drop in and out so quickly so as not to be caught by the board, resulting in no errors while stopping the cycle. But normally the inducer keeps on trucking with pressure switch errors, whether the board cataches them or not...?
Another idiosyncrasy we'll all be expected to remember, I suppose. I was tipping towards the board as well. Sometimes I think I should just jump all safeties one at a time when I get these weird ones, even thought it doesn't jive with what you are thinking as far as the normal sequence of operation. How long would it take? Few roll outs, a limit, draft switch, pressure switches...?
Professional Member*
Like to the the OP for returning to let us all know the final outcome. Thanks evilsanta.
So many of these head scratching posts just end up with no resolution.
Professional Member
Thanks OP for posting the fix. I had a furnace with a similar problem last week. It was dropping in and out intermittently, so another tech replaced the door switch. A week later I'm sent out on a follow up, talk to the homeowner she says it didn't work earlier today, but now it's working again. I check for codes don't see any, so I tape the switch everything works fine, put the door back on, here comes the problems again. I check the switch it's fine. I finally figure out that the r stat wire wasn't tightly screwed down, and whenever the door was put back on it would push the wire just enough so that it would intermittently lose contact.
Regular Guest
wiring harness
Professional Member
I had one years ago that I suspected had a bad pressure switch. After replacing it, and problem did not go away found a wasp nest in the flue pipe. Did I feel stupid over that. However I will never forget it. Now I stay away from residentual work, you guys can have it. Good luck and God Bless
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You have to let the inducer run for a sec before you jump it. Glad you got it
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A good lesson to learn is 90% of the time you get a pressure switch code it's not the switch. Maybe not 90 but close.
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It very well could be that the board is bad, however I have seen something similar to this. It is possible that there could be a low voltage short or a loose connection either on the board or in the wiring that wouldn't cause a fuse to trip, but to cycle like this.
Last summer I observed a short in a contactor coil. When the Thermostat (Honeywell 5000) would come out of its time delay and energize (Y) causing the short, the thermostat would flicker then cycle back into its time delay and never trip the low voltage fuse. I observed this happening about 4 or 5 times in a row. I ohmed the contactor out, found it shorted to ground, change the contactor, and everything was fine, we haven't been back since.
I would at lease make sure all your connections where good. and no nicks in the wiring. Just a thought.
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True story. I should hit refresh ever so often.. maybe I would have seen the end result.
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Professional Member
A lot of good troubleshooting info here. You guys do good work.
Professional Member*
I'm starting to think this might not be as true as it used to be, perhaps due to the increased presence of 90%ers and the water fouling contacts? Have to ask our neighbors to the north...
I've already caught a couple more this year over last on 80%ers.
Or maybe just like everything else...someone found a cheaper way to make junk.
Professional Member
I finished up a class last week with Johnstone on MODULES
Class was told that 99% of switch sent back tested A-OK
DON"T mess with the US
I thought I had been there and done That.
ITS ALL ABOUT LEARNIN!
I thought it would be better by now
"He who works with his hands is a laborer.
He who works with his hands & his head is a craftsman.
He who works with his hands, his head & his heart is an artist."
~St. Francis of Assisi
Professional Member
I,m wondering why the inducer does not continue to run even thou the pressure switch fails to close.
Seems to me its safer to have it run than stop,the board should then keep the ignighter from lighting,.
That would definetly make you look at pressure switch and igniter FIRST
Watching the Video Made me think like others that it was Power Related
DON"T mess with the US
I thought I had been there and done That.
ITS ALL ABOUT LEARNIN!
I thought it would be better by now
"He who works with his hands is a laborer.
He who works with his hands & his head is a craftsman.
He who works with his hands, his head & his heart is an artist."
~St. Francis of Assisi
Professional Member*
I agree. When P/S's fail to close the inducer keeps running till the board shuts it down and throws an error - takes a full minute and change on most furnaces. I'm assuming the pressure switch closed and then quickly reopened - prompting an immediate shut down. But this should not be. The blower and inducer should continue to run if the P/S breaks in the middle of a cycle. In fact, is it not even more imperative that they continue run if a safety opens in the middle of a cycle as opposed to the very beginning of a cycle? Matter of fact, the P/S is on the gas valve circuit along with the limits, rollouts etc and should have nothing to do with the inducer...
Dammit! I've second guessed myself back to the board and 1. it's not even my job & 2. the issue has apparently been resolved!
New Guest
Just curious, is this a 90% or 80% with an aux. draft induced motor vented horizontally. I have run into some bad wiring and pressure switches incorrectly wired on aux. draft motors and no barometric dampers that can really mess with primary inducer motor and pressure switch.
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