I have a hunter thermostat model 44860, and a central air heating a/c unit. The air conditioning system works fine. The heating side however does not kick on the fan in auto, I have to switch it to manual on then of course it doesn't shut off if I don't turn it off because it in on mode not auto? Is there a limit switch that's bad or wiring issue?

Found the problem, it was a loose wire. The connection between the rc/rh terminals was loose.

Glad you got it fixed, that would have been a hard one for us to help with. Good job.