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Matthew
Matthew, HVAC Technician
Category: HVAC
Satisfied Customers: 2014
Experience:  14 years experience in the HVAC field of service, installation, Manual J & D calculations
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the furnace ignites but the blower does not come on

Resolved Question:

the furnace ignites but the blower does not come on
Submitted: 6 years ago.
Category: HVAC
Expert:  Matthew replied 6 years ago.

either the motor is bad, the capacitor is bad, the fan limit control, or the blower relay is bad. Set your thermostat to fan "on" and the system switch to "off" then go down to the furnace. Take the doors off then press the door safety switch in so the furnace has power. If the blower motor is not starting up reach in and give the wheel a spin with your hand if the motor is fine and the capacitor is the problem then the wheel should spin freely and even try to start up when you give it the spin start. If there is resistance and you can not get the wheel to spin freely then the motor is seized up and you need a new one.

 

If the fan limit control is stuck then the blower will not come on try spinning this dial by hand to see if you can get the fan to activate. This limit has 3 set points on it. The first is the temperature at which the fan turns off after a heat call, the second is the temperature at which the fan shuts on for a heat call, and the third is the temperature at which the furnace shuts down the burners and continues to run the blower for safety reasons. This is what the fan limit looks like....

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The fan relay is the last thing and to check this you would need a voltage meter, but if all the other tests I gave you to try do not seem to be the answer then this is most likely the problem. This is a fan relay...

 

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