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Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 8511
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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blower and exhaust blower run all the time but the heat and

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blower and exhaust blower run all the time but the heat and air don't work, wondering if it could be the circuit board
Welcome to Just Answer!

Odds are in the 80% range or better that it is a circuit board gone bad... That would be because the blower should not run unless you have the thermostat set in 'fan ON' mode at the same time the furnace is running the combustion air blower.

When you see two malfunctions at one time it is not generally a peripheral device causing the problem.

Make sure that thermostat is not set on Fan ON, but on Fan Auto. Tell me if you are good as such things as appliance repair and working with electronics and what test instruments you have on hand.

We can go from there


Customer: replied 3 years ago.

the fan is in auto and the thermostat is off. I am ahandy man I repair all my on stuff

Thanks for the information, your guess that the control card is bad in this case is most likely accurate, 95% chance of that or better in this case for the reasons stated earlier.

buy an exact wire for wire replacement for the card, not one that requires you to adapt it.. that can be a problem in many cases.

If you wish to rate my advice so far positively, I will hold the question open on an unlimited time basis for any later follow up you might need.



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