I'm working on getting my old house ready to rent and have hardly been there the last month except for painting and such. The other day I switched the t'stat from off to heat and expected to hear the heater kick on fairly quickly. Nothing happened, so I double checked the program and then manually moved the temp up. Still nothing, I switched it back to cool and the AC kicked on when I set the temp low enough. Since the AC came on I'm assuming the access panel is good but I've taken it off and on a couple of times. I don't see any wires that are lose in the furnace. The LED in the little portal window was a solid red which I think means it is fine. I do hear a slight whine coming from the unit and there is a little wheel spinning slowly as long as the power switch is on. Earlier in the summer the AC died and was replaced, along with a new t'stat. I pulled the cover on it and looked like the dip switches were set right and the wires hooked up. Since it is a 30 mile drive I'm hoping to get some ideas to check and hopefully fix myself before I have to wait for a 4 hour repair window at an empty house It is a Carrier 58sta/stx that was installed by the builder about 6 years ago. I checked and the gas valve is on and I didn't see anything else to look at.