Keeping Your AC System Cleaner

How To Replace A Furnace Door Switch

by Yolanda White

A furnace blower fan sucks in the air coming from the intake vents in your home, pushes that air over the heating element, and then helps cycle that air back out the vents in your home. The blower fan compartment has a door switch as a safety feature. The switch switches off the fan if the compartment door opens so that wiring doesn't get sucked into the fan. A broken door switch can prevent the fan from running at all, which would also prevent the furnace from working.

If your furnace has recently stopped working, you can check to see if the door switch is broken. Replacing the broken door switch is a quick process that only requires a screwdriver.

Things You Need:

  • Screwdriver
  • New Door Switch

Step 1: Remove Old Door Switch

Shut off all electricity to the furnace by switching off the circuit breaker or the appliance on-off switch located near the furnace.

Locate the upper and lower access panels on your furnace and look to see how the doors fasten on. Either remove the screws or twist the knobs that are holding the doors in place. Set the doors and fasteners somewhere safe while you continue with the project.

The dividing section between the two panel doors is still attached to the furnace. Use a screwdriver to remove the screws holding that dividing panel in place and then remove the panel.

Locate the door switch. Disconnect the wires attached to the switch. It's easy to see how the wires reattach so you don't need to remember the orientation of the wires. The remaining door switch has a tab on each side. Push in those tabs and then pull the switch out of its hole in the furnace frame.

Step 2: Install the New Door Switch

Place the new door switch into the hole by pushing in on the tabs until it's in position and then releasing the tabs. Reconnect the wires to the door switch.

Put the dividing panel back into position and reattach its screws. Put the lower access panel on and tighten its fasteners. Put on the upper access panel door and tighten its fasteners.

Restore the power to the unit and then use your thermostat to actually start up the heating process. Check to see if the furnace is operating correctly. If the furnace is still malfunctioning, you might need the assistance of a HVAC repair technician.