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albert1985 · Jan 22, 2011, 11:05 AM

Rheem model rgda 075a cr.replaced thermostat cleaned heat sensor.. no change.. next step was replacing heat sensor but unsure were and what sensor to buy."ANP001FS Universal Flame Sensor Electrode" appears to be a match(visually) to the one it cureently has.. but that is online.. any advice would be greatly appreciated

mygirlsdad77 · Jan 22, 2011, 12:44 PM

By pilot, do you mean the glow plug is glowing, but the burners never ignite, not even for a second or two? Or do you actually have a pilot light? How old is the furnace? If its hot surface ignition(glow plug) and the burners never ignite, then the flame senser is not the problem, as the flame senser has to have flame present to work. I would suspect the pressure switch that sends power to the gas valve is not being pulled closed. Check for 24v to gas valve while glow plug is glowing. If no power, check to see if you have 24v coming into both pressure switches, and 24v going out of both pressure switches while the draft inducer is running.

albert1985 · Jan 23, 2011, 01:52 AM

Furnace is circa 1989, it has a pilot burner flame which stays on. From research I've found the heat sensor is actually thermocouple. Does this still rule this part out? Earlier I removed thermocouple and pilot would not remain on without thermocouple, my friend suggests this means thermocouple is working properly but online info suggests pilot can stay on and while thermocouple is defective and does not create electric signal for gas to be suplied to main burners. I will check for proper volts today.given the type of furnace that I have, does it have a pressure switch? The furnace does not make any sounds motor does not come on at all unless fan is set on "on" on thermostat, but burners remain off

mygirlsdad77 · Jan 23, 2011, 11:46 AM

Hi. Okay, you have a standing pilot. The pilot remains lit, so the thermocouple is fine. Next step is to check for voltage to gas valve. If none, then trace back the wiring from the gas valve through any high limits and see where you are losing voltage. You may need to call in a pro to trouble shoot the furnace. Please let me know if you have voltage to the gas valve when there is a call for heat from the thermostat. Your unit does not have a pressure switch if there is no draft inducer motor. Maybe if you could post a pic of the inside of your furnace I would tell you what to check next.