Furnace issues

[Rosieriviter]

When I set thermostat control to heat my air conditioner tuns on with the furnace??
Both run the (AC fan not the compressor ) Outside temp 29 Inside 45. Furnace set on 70. How do I shutdown the AC fan. @2013 FB 25 flying cloud. New to this unit

[DKB_SATX]

I'm not 100% certain this is the issue you're having, but I'd guess 2 things are going on here. You're probably in "Auto" on the thermostat, with the fan set to be constant-on rather than auto. It doesn't seem like it should do what you're describing at those temps, but it's my first guess.

Make sure the thermostat is set to "FURN" rather than "AUTO" (and check your fan settings) and see if that improves its behavior.

[Mattirs]

Adding DKB, you also might have it set on heat pump which Will Not work at that temp. That cold make sure you are on Furnace thus using propane.

[Rosieriviter]

Thanks for the input. Followed your suggestions. No luck, so I opened the AC breaker, problem solved (for the winter anyway).

[Wayne&Sam]

I had this same situation. a few years back. It should be what David said. If the fan speed is set to something other than "Auto", the fan of the AC unit will come on with the furnace. Switch the fan speed to "Auto" and you'll be fine.