I have a Rheem 100k BTU gas forced air furnace.
With the thermostat calling for heat the unit fires off fine, then 30 seconds later the blower turns on.
The unit will operate for only another 30 seconds or so and then both the gas burner and blower shut off.
The unit will repeat this cycle in another 3 minutes or so.
I've checked the draft in the flue (it's strong) and just replaced the limit switch, but it still operates the same.
Any suggestions for the next step?
Thanks in advance!Dave
Brian:Thanks for the prompt response! We've ruled out the limit switch, but here's another clue. When the flame goes out the blower keeps running, but only for another 3 to 5 seconds. That probably rules out a grounding issue, right?
You mention "check the sensor (measure microamps)" but I'm not sure which sensor you mean. Can you advise?
Thanks again for your patience and advice!Dave
Thanks for the updated responses!
The unit is an older Rheem. I decoded the serial number and I think it was manufactured in 1992 or '93.
It's a basic 'builder's model' and as I recall the unit isn't very efficient (about 70 to 72%) so it may be worthwhile to upgrade to a newer unit and be done with it!
I'll check the voltage to the leads as mentioned and see what's up. I will probably then get a local tech to check it out as I'm about at the end of my DIY abilities.