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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8373
Experience:  Furnace, A/C and heat pump specialist.
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G4ra072c-12 will cycle 1-6 times then power has to be turned

Customer Question

miller g4ra072c-12 will cycle 1-6 times then power has to be turned off for 10-20 minutes for it to restart. there are no codes flashing on circut board.
Submitted: 11 months ago.
Category: HVAC
Expert:  airheatman replied 11 months ago.

When it will not fire, we have no code although calling for heat?

Customer: replied 11 months ago.
that is correct ,thermostat clicks on for heat but furnace does not respond unless I shut the power off for a.period of time. I suspect the power supply to the circuit board may be failing. just a guess. are there voltage parameters I should look for? one other thing I noticed - the blower continued to run after cool down but it only happened twice over several weeks.
Expert:  airheatman replied 11 months ago.

This all sounds like a failing control board

Customer: replied 11 months ago.
the circuit board was my first guess but the furnace cycles normally when running for however long it does. that is why I suspected the step down transformer that has been humming away 24/7 for decades. do you know of a good source of parts for the older miller furnaces? I have had some problems with internet & e-mail lately. Joe
Customer: replied 11 months ago.
waiting for reply
Customer: replied 11 months ago.
I do not want to replace the control board that functions normally if the problem may actually be the boards power supply , note the time period with power off before furnace will resume cycling.
Expert:  airheatman replied 11 months ago.

I will opt out to see if other experts have other ideas.