I have a similar problem. I have an old Honeywell mercury thermostat that activates the forced air unit for both heat and AC. Last week the kids ran the heater and since then the blower won't turn off. The heater and A/C still work if I set the thermostat correctly, but even when the heat or A/C stops the blower still runs. I have unplugged the unit and plugged it back in and that didn't work. I have removed the front panels and banged lightly on a few of the switch boxes. That did not work. Any suggestions before I call the HVAC man?

Check the bottom of the stat looking for a switch label ON/AUTO, make sure it is switched to AUTO and not ON. Kids do funny things sometimes

Hi b1, thanks for the quick response. On the stat, the switch is on Auto. We have the "H" all the way down to 50 degrees and the "C" all the way up to 90 degress. I can't decide if the problem is with the thermostat or with the forced air unit.

You could disconnect the wires to the back of the stat. Careful to make yourself a little "map" so they can all go back to where they were. If all wires are disconnected and the fan still runs you know it isn't the stat

B1, that's a very good suggestion. I'll try it and let you know.

Fan control is stuck

B1,

I disconnected the stat and plugged the fan back in and the fan started up again. It's the fan. Time to call the man. Thank you for your assistance. Its appreciated.

"plugged the fan back in " can you tell me more about what you just said, a furnace fan does not have a plug.

B1,

My central air unit looks like a two-part unit. The top section is a gas-heater and the bottom section is a blower. The entire system is plugged into a wall outlet. Because the blower will not turn off, I have turned off the gas line and unplugged the unit from the wall plug.

I just have never seen a central ac that plugged into a wall out. This is 240 vac, right?

It looks like a normal 3-prong wall outlet. I couldn't tell you if its 240 or not. I just know that I can unplug it and it shuts off. I know that sounds illiterate but I am not mechanically inclined. I was hoping that it was something simple like a reset button, but it seems a little more complex and I am really not qualified to start tinkering with the system. And of course my wife is concerned that if I start messing with it I will blow the house up.

If the fan will not shut off, it is either a fan relay, or a t-sta problem. Post a pic of your unit