Why does my Furnace Fan not work when thermostat is on?

Example: If the furnace was originally controlled by and wired for a Honeywell R7284 limit control and if that control was replaced by a Honeywell R7184 limit switch, the latter has no “LIMIT” wiring terminal. An installer may have spliced the original red limit wire in to the new R7184.

Can a Furnace Fan be set to auto?

Make sure your fan is set to AUTO and not ON. If your fan is set to ON, it will run continuously, regardless of whether your furnace is heating or not. Tip: Avoid setting your fan to ON, it wastes money because it forces the fan motor to run constantly. If your furnace fan is set to AUTO and is still running, then move on to the next section.

Where is the fan limit switch on my furnace?

If your furnace fan is set to AUTO and is still running, then move on to the next section. Your fan limit switch is located directly under your furnace hood and controls when your furnace blower turns on and off.

When does a Furnace Fan need to blow?

When your thermostat is set to AUTO, your furnace fan should blow only when your furnace is in the middle of a heating cycle.

Why does the fan turn on when the furnace is on?

This will cause the fan to automatically turn on when the furnace is heating and shut off once the call for heat stops. If your fan limit switch was already set to AUTO (not pressed in), then you most likely either have a problem with your thermostat wiring or the fan limit switch is bad.

Can a blower fan work only when the thermostat is set to fan on?

Fan will work only when thermostat set to fan on. Thank you for the question, Anon, as it’s a common A/C, or heating fan operating problem that needs to be understood: I put it as “The blower fan runs only in the MAN-ON switch but won’t run on AUTO”.