I have tried to replace a conventional lever action mercury thermostat with a new digital programmable Noma thermostat. The problem is when it turns on the heat and fan works fine but when it reaches heating it shuts of but the fan stays on and will not shut off:confused:

The model number of your new thermostat,the model number of your old thermostat and the wiring sequence for both will be needed so I can look them up.

Check to be sure your thermostat is set to automatic instead of on for the blower circuit before you go to all the above trouble. It could be as simple as the thermostat blower switch being ON and causing the blower to run all the time.

If it is not the on switch or the programing, go the sticky at the top of the forum. Between it and the manual t at should have come with the thermostat, you should find your problem.