I have a York P2MPD14N08001B furnace that occasionally does not follow correct power up sequence, the end result is that it blows cold air with burners off. When it does not work correctly, the blower turns on right away. The glow plug ignitor tries to heat up, but then cuts off shortly thereafter. The gas never turns on, and the blower will continue forever until furnace is reset. Initially a single reset will clear it out, but the problem seems to get worse as time goes on. Furnace repairman replaced pressure switch last year, and said if that does not fix it then the control board must be at fault. Once he replaced that(middle of winter), it worked great for a couple weeks, and then the fault came back, increasingly as time went on. At the end of last winter, 1 reset out of 20 would finally get the furnace to follow the correct sequence. After being off all summer, it worked perfectly for about 2 weeks. And now it is repeating the fault more and more often again. The fault LED has been broken off by some repairman along the way, so that diagnostic tool is unavailable.

Sorry for the wordiness, but any help would be appreciated! I could get the board and replace by myself, but am trying to avoid wasting $200 if that is not the problem.

Thanks!

mtngrwn

To clarify, the repair replaced the pressure switch only, not the control board. Furnace has original control board as far as I know.

Joshdta

sounds like a control board problem to me.

KC13

I'm starting to sound like a broken record...have you tried bypassing the thermostat? Connect "R" and "W" wires directly together and report result observed.

mtngrwn

Should I connect the wires together when it cycles up incorrectly? Right now, it only cycles up incorrectly about 3 times a day, but it is increasing from 2 weeks ago when it ran perfectly at all times.

I've went through 2 programmable tstats and am on the most basic non-programmable unit that Honeywell makes, I believe eliminating the tstat as the source of the problem.

I work with electronics, and I can tell you the control board was sloppily made. Component leads were touching each other under the conformal coating. Even so, it worked for 10 years before I started seeing problems. The age of the furnace is 14 years I think.

KC13

Indeed, most functions are timed, and old resistors...just can't put up a fight like when they were younger...members of 'the Resistance'...

mtngrwn

I don't suppose there is anywhere I can find a schematic for the control board? I did an internet search and couldn't find it with the p/n on the board. Unless it's the PROM IC on the board, I could probably fix it with the schematic. Johnson Controls is the manufacturer of the board.

Thanks for your input guys...