Rudd UGPH-12EARJR intermittently flames out

Old 12-11-21, 12:44 PM
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Rudd UGPH-12EARJR intermittently flames out

Furnace intermittently short cycles. Draft motor starts, igniter glows, main gas valve turns on, main burner lights, and blower motor turns on. Furnace runs fine for random period of time (few minutes to an hour+) when the flame goes out (all with thermostat set higher than current temp). Furnace tries to restart by turning on the igniter and turning on the main gas valve. This may or may not be successful. If it is unsuccessful, there is no gas even though it sounds like the gas relay operated, and the furnace will attempt to repeat this, which might be successful or unsuccessful until it locks out. If at any time it is successful, the furnace will run fine for a random period of time until it flames out and the restart cycle starts again or the thermostat temperature is reached.

I cleaned the flame sensor even though the amber flame sensor on the control board is always lit solid when the flame is present. I checked the 24vac through the main limit control, rollout switches, and vent safety control and they appear fine. It has a heat-assisted limit control, which I replaced, but it had no effect. I replaced the IFC (control board) also without any affect.

Then I noticed that when the flameout occurs, there is still 24vac on the main gas valve for a second or so before the IFC shuts the voltage off. This was an eye-opener, as it pointed to the main gas valve as the issue (it was difficult to observe, as I had to stare at the dvm connected to the gas valve until the flameout occurred at some random time). I subsequently observed that when the furnace attempted to restart and if it failed, at the point when the relay clicked to turn the gas on, 24vac appeared at the gas valve, but the gas did not start and the furnace would recycle. If the restart was successful, when the 24vac appeared on the gas valve, gas would be present and ignite.

At this point, I feel it is the main gas valve, but I am looking for a second opinion. The valve is marked 36E37 214 and 60-23490-01. I seem only to be able to find used ones on eBay and I would rather replace it with a new one. I found a site that says 36E37-214 is obsolete and is replaced by 60-24180-81. Furnace is 26 years old but in pristine condition.

Hoping to confirm main gas valve is issue, and what the correct replacement is. Thanks!!

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