Comfortmaker RPJ2 Trouble

tpope

Hello,
Today I am working on a Comfortmaker RPJ2 furnace. Initial problem was no heat with the 2 blinking lights indicating the pressure switch was closed. Upon inspection, the draft inducer housing had a crack, its motor bearings were also excessively noisy, and the vacuum hose to the pressure switch had a small crack. Ah.. an easy repair. Replaced all of the above; new draft inducer motor & housing, new pressure switch - following the new pressure switch's instructions to adjust the switch to .90 WC per the original pressure switch spec (original switch was set at the factory). One would think we're done! Heck no... The furnace cycled nicely about 2 or 3 cycles and then locked out with 2 blinking lights - "pressure switch closed" again.. just like before all of the new parts were installed!!! Upon disconnecting and reconnecting the power, the draft inducer starts as soon as power is connected and runs continuously (regardless of if the thermostat is calling for heat). Any ideas on this one?? Best regards, Tom

Addition: I forgot to add that the vent is clear to the roof (no leaves, etc), the filters are new and clean, and thermostat seesm to be functioning normally.

coolmen

you say the inducer runs even when not calling for heat. disconnect W from the control board, this tells us if its thermostat or low voltage wireing malfunction. if problem still occurs replace control board

tpope

Coolmen, Team,
I followed the advice this evening, diconnected the white wire from the control box. With W disconnected, I switched the unit on and the inducer started up immediately. If I follow Coolmen's logic, this should mean that the thermostat was not allowed to call for heat (disconnected W) and the inducer still kicked on - so something is wrong with the control board. Correct?

Now, here is a follow-on question. Upon fiddling with it today I had a better flashlight with me - and took a look inside the burners. Looking down the burners it was apparent that the metal blades down which the flame travels are a bit burned up - burning away at the tips with bits of metal bubbled up at the ends. Should I stop here and replace the furnace before I buy a control board?

#CARRIERMAN

Hi tpope

The unit you are working on should be electronic ignition. This being the case it may have either a Fenwal control or a United Technolgy. If this is the case it sounds like your ignition control is bad, which also controls inducer. The other possible set up for this furnace is a Honeywell smart valve II. If this is the case, grab your bucket of vasoline and get ready. If it uses the smart valve set up the only way to fix it is replacing the gas valve. Whichever set up you have, for some reason the ignition control has failed, this is the reason for the nuessence problem.

Good luck
Rusty

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