[GeezerJohn]

I have a forced air HVAC unit that gets heat from the hot water tank. There is no limit switch on the fan -- it comes on with the heat. Last week the thermostat would not shut off the heat whether I reduced the temperature setting or switched it off. When I switched it to cool, both the heat and AC ran. I pulled the thermostat off the wall and the heat stopped. Replaced the thermostat and it worked fine for about 5 days. Now the heat is running nonstop again. The only way to shut it off is at the breaker. Before I call Honeywell to blame the new thermostat, I'm thinking there must be something in the wiring or HVAC unit.

[Wigtail]

Check the voltage to your thermostat. It may be too high and burning the thermostst up. It should state the voltage on the transformer. Never seen it before but...