When I turn on my central AC, the furnace fan starts up and runs for a
second or two then shuts down. The diagnostic led on the controller
indicates Normal - no heat call.
The outside compressor unit continues to run, without the furnace fan
I turned on the heat, and it works ok.
Does anyone have a suggestion on how to troubleshoot this further?
If the motor works fine for heating, its not the cap.
If you have a switch for the fan on your T-stat, set it to "on" and see
if the motor comes on. Then adjust the T-stat so the A/C comes on,
leaving the fan switch on. If the fan continues to run, there may be a
problem with the wiring of the T-stat which prevents the fan from
coming on in the "auto" setting.
The fan will run if the thermostat switches are: Fan-On+Cool/Heat -
Off, Fan-Auto, Cool/Heat-Heat. As soon as I switch the Cool/Heat to
Cool, no matter what the Fan setting is at, the Fan shuts down. If I
turn the cool/heat Off, and have Fan-On, the fan won't come on until I
switch the Cool/Heat to heat. I took the thermostat out of the picture.
If I hook Red-Green - Fan comes on, If I hook Yellow-Green - Compressor
comes on. As soon as I add Yellow to Red+Green the fan shuts off.
My final troubleshooting attempt...I moved the blower fan motor wires
around to try and
use a different fan speed for the cooling function. No help..it behaves
the same on all speed positions. I'm thinking that its the circuit
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