Blower not running in A/C mode but works on heat mode

Old 03-18-20, 12:11 PM
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Blower not running in A/C mode but works on heat mode


I have a Bryant 313AAV HVAC system and when switching the system to cool mode lately the blower is not operating. AC is operational but blower does not turn on, it also doesn't work when trying to manually trigger the fan.

However it does work in heat mode or when manually triggering this in heat mode. Is this likely a failed resistor and do you recommend replacing the circuit board or is there something else I should try first?

Per Bryant system is not under warranty for parts as I purchased the house from another owner so warranty period was reduced in half.

Pics attached of S/N, wiring diagram and circuit board.

Thanks in advance for any help or guidance here!


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Old 03-18-20, 04:08 PM
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Welcome to the forums.

Look at the highlighted part of the diagram. That's the low voltage control for your electronically controlled motor. You will need a meter to measure for AC voltages.

You'll need to measure from.......
green to blue (COM - HEAT) for 24vAC in heat mode.
green to gray (COM - COOL) for 24vAC in cool mode.
green to red (COM - FAN) for 24vAC in fan on mode.

Let us know what you measure at each location.

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