Burner igniting but quickly goes out.

johngu99

Earlier this year, my10 year old York gas furnace with 2 stage gas valve and ecm2.3 blower motor stopped working during the summer A/C season. After troubleshooting, I concluded the that the blower motor was bad. I was quoted over $ to replace the motor by a local contractor. A coworker who is licensed to do HVAC gave me a used 1/2 HP PSC motor and a relay and told me how I should install it. I used the 24volt green blower wire coming from my thermostat to control my normally open relay. Success! The furnace/AC combo worked flawlessly all summer.
The weather is getting colder now, so yesterday I tried running my gas furnace for the first time since I replaced the motor. With the T-stat set to heat and the fan set to auto, the T-stat is calling for heat, but the blower doesn’t turn on. When I set the fan to “ON”, the blower comes on, then the ventor motor blower comes on, the hot surface igniter glows orange, the gas valve clicks and the burner lights. After 2 seconds, the burner shuts off and the furnace tries again another 2 times until it locks out for an hour. I pulled out the flame rod and cleaned it up with a scotchbrite pad, but the burner still won’t stay on.
Is it possible the main control board is waiting for a signal from the ECM motor confirming that the circulation blower is on ? I could not find an air-proving switch anywhere on the blower housing or on the adjacent ductwork. Could the removal of the ECM motor be the cause of my failed combustion? I was considering purchasing a Qwikswap V3 adapter board which claims to properly adapt from ECM to PSC motor while still maintaining the ability to control your PSC’s 3 motor speeds. I’m not sure that a Qwikswap V3 conversion board would address the issue of missing feedback signal from the original ECM2.3 motor. Any ideas on a solution to this problem would be appreciated. Thanks!

Ironman

You probably have two separate issues:
1. The board is not sensing ignition. Check all of your ground connections in the furnace and all the way back to the panel. You may have eliminated a ground path when you replaced the motor. There’s no signal sent to the board from the motor. Also, the flame rod should have been cleaned with a dollar bill, not a scotchbrite pad.
2. If your relay setup only involved connecting the green wire, you won’t have any blower in heat. There’s more to converting to a psc motor than most realize and a simpler high tech solution would be using a universal ECM replacement kit.

EBEBRATT-Ed

Another relay with the coil wired to W & C off your stat and the contacts wired in parallel with the ac fan relay would get you going. Maybe not the best way.

The ignition problem is probably unrelated

Ironman

How did you determine that the original motor was bad?
It could have been the board was bad and you bypassed that with a relay but now it’s not sensing ignition.

mattmia2

Ironman said:

How did you determine that the original motor was bad?
It could have been the board was bad and you bypassed that with a relay but now it’s not sensing ignition.

Or the board just wasn't powered for some reason.