Furnace Relay Switch Problem

You may have to check a few areas to eliminate this as a problem.

Furnace relay switch problem.

Check the emergency switch usually located near the furnace room. Move the thermostat mode switch from cooling to off and move the fan switch from auto to on let the blower run for at least 30 minutes or until there s good airflow at the registers. Turn off electrical power to the heating system reconnect the fan motor where you previously disconnected it turn on electrical power to the heating system call for heat. Switch it back on and see if this corrects the problem.

Many times wires are either loose or burnt behind the fan center relay. Then turn the ac back on to test it. A switch inside the door compartment engages when the door is closed properly. Move the lever on.

First make sure your furnace power is turned. Furnace blower fan wont turn off fan select switch on the thermostat is in the manual on position a control wiring problem where the insulation on the wiring is worn off a bad relay fan sequencer relay fan limit control or circuit board with contacts sticking this depends on the type. If the fan limit switch worked normally continue as follows. But another problem that occurs just as frequently from a faulty relay is that the heating elements and the blower fan will refuse to shut off.

If it works for the next 12 hours you ve solved the problem. Make sure that your furnace switch is on the furnace blower compartment door is on and secure. Furnaces require electricity to operate oil pumps thermostats internal electrodes relays and other electrical components. That is definitely one possibility.

If this isn t the problem you can reset the power by switching the furnace off at the furnace power switch for about a minute. Set the building thermostat to call for heat. Verify the furnace door is closed fully as an open door will cause the furnace not to work. The reason for this is that the relay could become welded into the closed position and continues to allow power through to the heating elements and the fans.