The fan in the attic is not blowing with the a/c on (the compressor will run outside) or if I just turn the fan to on on the thermostat.

However, it will run if I turn on the heater.

Suggestions?

Thanks!

Most likely, something in the fan control circuit has failed (t-stat fan switch, fan relay, or wiring between the two). Heat relay usually controls fan in heating mode.

Thank you for the quick reply!

And are those issues that you mentioned relatively inexpensive to have fixed?



Most likely, something in the fan control circuit has failed (t-stat fan switch, fan relay, or wiring between the two). Heat relay usually controls fan in heating mode.

Relative to cost of system replacement, yes. Relative to cost of lunch at McDonald's, no.