A pressure switch is a safety sensor inside your heating and air conditioning unit that checks to make sure the proper air pressure is present for combustion gas ventilation. If the air pressure isn't present, the switch will keep your unit from turning on because the combustion could either fail or cause harmful gasses to release into your home.
If the pressure switch breaks, the furnace will either start shutting off quickly after starting or will fail to turn on at all. You will need to rule out some other common issues such as the pilot light, igniter, or capacitors but if you know for sure the pressure switch broke, switching out the part is easy.
What You Need:
- New pressure switch
Step 1: Remove the Old Pressure Switch
Shut off the power to the furnace using the shut-off switch, circuit breaker, or fuse. Locate the upper access panel and its retaining knobs. Twist the knobs to loosen the panel then lift up and out to remove. Look inside the top access area, and you will see the pressure switch.
Disconnect the wires from the pressure switch by just pulling firmly on each wire. You don't need to worry about memorizing the orientation of the wires as the order and positioning of the wires is relatively self-explanatory.
Use a flathead screwdriver to pop the pressure tube out of its tab at the bottom of the switch. Allow the tube to hang in place until you install the new switch.
Use a socket to unthread the mounting screw holding the pressure switch to the furnace. Pull the switch forward to remove the broken part from the heater.
Step 2: Install the New Pressure Switch
Pull the new pressure switch out of the box and confirm that the pressure rating on the new model matches the rating on the part you just removed. Now you can safely discard the old pressure switch.
Slide the new pressure switch onto the mounting bracket. Thread the mounting screw through the holes and tighten into place with a screwdriver. Attach the gas switch wires to the appropriate terminals. Slide the pressure tube into the proper spot on the bottom of the switch.
Replace the upper access panel by aligning the top edge first then pressing the rest into place. Twist the retaining knobs to secure the panel in place. Restore the electric supply to the furnace, start the unit, and make sure the part switch fixed your problem. If the unit still doesn't run properly, call a heating and air conditioning repair company, such as Jackson Heating & Cooling, for help.