I just installed a NOMA 7-day programmable thermostat for an electric furnace/AC system (ceiling unit). I believe the wiring (5-wire) is correct.

When I set it to COOL with Fan set to AUTO, it turns on the A/C and the fan automatically. Good.

But when I set it to HEAT with Fan set to AUTO, it turns on the heating system but the fan doesn't. The fan does turn on when I force it by setting the switch to ON.

Any idea why?

The heating mode uses a different winding in the fan motor controlled by a different relay than cooling or fan on. The controls activate the relay a timed delay after getting a signal the gas is on. You could have a problem with the controls, most likely the relay, or the flame sensor, or the fan motor. Finding a point to check each component can be tough. Does your furnace give trouble codes by flashing a light?

I found out I had the wrong settings on my thermostat. I have to change setting HG (gas) to HE (electric) because the electric furnace will not turn on the fan automatically. The thermostat has to force it ON.

HE setting is needed for electric furnace. HG is for gas furnace which will turn on the fan by itself.

Changing this same setting also worked for me. The fan would not run unless I changed from Auto to On. But after making this change, mine also now works.

The blower on my furnace will not kick on at times .

The blower on my furnace will not kick on at times .

Please post this in a separate thread and provide make, model # and serial #.

I found out I had the wrong settings on my thermostat. I have to change setting HG (gas) to HE (electric) because the electric furnace will not turn on the fan automatically. The thermostat has to force it ON.

Joined to say,after 2 years and 3 different A/C mech .I followed your advise.Fixed my furnace problem. Thanks,:D

I checked the thermostat fuse and it appears to be good, and the HG Switch is in correct position, and the fan does not engages in either the "auto" or "ON" (manual override) positions. One person thought it might be the "High Limit Switch," however how do I confirm. Like the person above, the fan DOES COME ON for the Air Conditioner, just NOT the HEATER. Any words of wisdom? Thanks in advance.

New Honeywell TH6110D thermostat does everything it should to run the gas heater.
But it does not turn on the air conditioner, nor will it run the fan in manual fan mode.

By removing the thermostat from its base plate, I can run the fan by jumpering G and C (24v common terminal). And can start air conditioner compressor by jumpering the Y terminal.

I have gone through the settings of the thermostat several times for correct setup.

New Honeywell TH6110D thermostat does everything it should to run the gas heater.
But it does not turn on the air conditioner, nor will it run the fan in manual fan mode.

By removing the thermostat from its base plate, I can run the fan by jumpering G and C (24v common terminal). And can start air conditioner compressor by jumpering the Y terminal.

I have gone through the settings of the thermostat several times for correct setup.

Hi
Remove the C wire
Connect a jumper between Rc and R and Tape off the C as C is comman and is only used for the power to display