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Discussion Starter · #1 ·
I'm receiving a pressure switch error code on my Trane furnace. This issue seems to be intermittent, but not getting frustrating.

To date I have removed the trap ( washed it out ), blown thru as many hoses as possible, and removed the intake and exhaust ( blowing each out with a dry vac.

The crazy issue is that the furnace will run perfectly for a few days, then start tossing the error code, again. A week ago, I removed the pressure switch vacuum line that goes to the burner box...the furnace fired and ran perfectly...which I assume, it should not have fired.

Anyone ever been confronted with an issue of this nature & what could possibly be the problem? Also, my CO detectors have not detected anything. Wouldn't they sound off if there was an issue with the heat exchanger?

Thanks for reading & look forward to responses.

Jim
 

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That switch have 2 vacuum lines to it? You either have something stuck in your fresh air intake, or something is wrong on the venting side. Check for birds/nests/leaves etc in both intake and exhaust venting.

Cheers!
 

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Discussion Starter · #3 ·
Correct, it has 2 vacuum lines to the pressure switch. One vacuum line to the burner box & one to the secondary heat exchanger. I removed both the intake and exhaust & blew through both PVC pipes with a dry vac for about 3 mins. Any debris was not noticed.

Also, installed the exact numbers matching pressure switch with the same results (pressure switch error-3 blinks).
 

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Discussion Starter · #6 ·
How old is this furnace? Does it run with the burner box cover off?

Cheers!
Just wanted to add a bit of other information...perhaps, it has some relevance. There are (2) rubber hoses that attach to the top of the drain trap. One hose ( which is smaller in diameter ) goes to the inducer motor & the other larger diameter hose goes to the secondary heat exchanger.

Also, there's a hose exiting the p-trap that goes directly into the condensate pump. I removed the drain hose that fits inside the condensate pump and blew into it. I heard gurgling & was wondering if this is normal. Also, do these p-traps go bad and could it possibly cause the dreaded pressure switch error code.

Thank you!
 

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I just had this exact same issue with my furnace. Furnace would run great for a while and then random pressure switch shut offs. I had a fairly large hole ...about 2" in my heat exchanger and none of my C02 alarms ever went off. I think because I have a draft inducer. My advice...open up the furnace and inspect for a crack or whole...not worth the risk.
 

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I just had this exact same issue with my furnace. Furnace would run great for a while and then random pressure switch shut offs. I had a fairly large hole ...about 2" in my heat exchanger and none of my C02 alarms ever went off. I think because I have a draft inducer. My advice...open up the furnace and inspect for a crack or whole...not worth the risk.
Not the biggest I've seen, but I'm surprised that it was still running. Usually by then it's tripping the roll out switch. (unless your pressure switch was in series with the roll out)

OP: Gurgling isn't so normal, but some condensate will be in those tubes. As long as they aren't plugged, you should be fine. At 8 years, there may be a crack in the heat exchanger or the secondary is plugging up. You need to measure the pressure at the switch.

Cheers!
 
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