Furnace Relay Switch Problem

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.

Furnace relay switch problem.

You may have to check a few areas to eliminate this as a problem. Furnaces require electricity to operate oil pumps thermostats internal electrodes relays and other electrical components. If the fan limit switch worked normally continue as follows. 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.

Verify the furnace door is closed fully as an open door will cause the furnace not to work. Switch it back on and see if this corrects the problem. Many times wires are either loose or burnt behind the fan center relay. That is definitely one possibility.

Check the main circuit breaker entrance panels and any fuses or circuits found in the furnace itself. Check the emergency switch usually located near the furnace room. Make sure that your furnace switch is on the furnace blower compartment door is on and secure. A switch inside the door compartment engages when the door is closed properly.

Set the building thermostat to call for heat. With the furnace on use a. 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. 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.

Turn off the furnace at. 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. First make sure your furnace power is turned. If it works for the next 12 hours you ve solved the problem.