[Tom R]

I just installed a new thermostat last spring and everything was fine until I had to turn my furnace on for the first time. (My furnace is a Janitrol forced heat) When my furnace kicks on, I notice that my outside ac unit also kicks on. Does this sound right? Or could it be a wiring problem in my thermostat or something else?

[ballengerb1]

You probably wired your stat incorrectly. Did you jumper the two reds, Rc and Rh? You do this if you have only one transformer. Did you have both a yellow and a white wire coming from the furnace? What model stat did you use?

[acetc]

If this is a digital electronic thermostat, you may have it set up for heat pump operation and not gas electric, you may have a switch to move over or tell it in the set up that you have a gas electric. Good luck, Mkie

[Tom R]

You probably wired your stat incorrectly. Did you jumper the two reds, Rc and Rh? You do this if you have only one transformer. Did you have both a yellow and a white wire coming from the furnace? What model stat did you use?

Thanks for responding! I did jumper the 2 reds. I do have a yellow and white wire coming from the furnace. The model is a LAX. How should I rewire it?

Thanks for being so helpful. You have me on the right track. For now, I just pulled the fuse on the AC unit outside.

[Tom R]

Put me on the right track

[labman]

There is a very complete explanation of wiring up thermostats at https://www.askmehelpdesk.com/heatin...ons-58313.html

Did you check Acetc's idea? I find that far more likely than being miss wired. I can't see how you could wire it so the A/C ran OK but you get both it and heat on heat.