Residential Plumbing & HVAC Experts

Your Furnace Has Quit on You? Simple Troubleshooting That Might Get It Going Again

With the cooler months upon us, every homeowner should run through his or her checklist for fall maintenance. But what happens when something goes wrong, despite your preparations, and your furnace breaks down? Try these eight simple furnace troubleshooting tips before you make a service call.

  • Make sure that the thermostat is set to “On” and “Heat” and is displaying the correct date and time (if you have a programmable model). For programming problems, enter your desired temperature and press “Hold” to switch the furnace on.
  • Check the wall switch on or near your furnace. Then, inspect the circuit breaker and fuses.
  • If your blower is running, but no heat is coming out, replace the air filter. Your owner’s manual will show where and how to replace it. Check to make sure the pilot light is lit and the burners are flaming.
  • Follow the gas line to the meter. If the handle is perpendicular to the gas pipe, turn it to be parallel.
  • Turn off the furnace and thermostat, and take apart the duct where it exits the furnace to clear it of debris. When finished, put everything back together in the same order.
  • For high efficiency furnaces, if the drain is dirty, remove the hose and fill the drain with a mix of one part bleach to three parts water. Flush repeatedly.
  • If only some rooms are cold, check that the registers are open and inspect visible ductwork. Seal any gaps metal tape or mastic sealant. Make sure that handles in the ductwork, which are dampers or bypasses, are open.
  • Clean off any outdoor furnace intake or exhaust vents. If you have a heat pump, clear debris away from the compressor unit’s fins.

If none of these furnace troubleshooting fixes work, or if you feel uncomfortable doing them, your furnace doesn’t need to remain a mystery. Please contact us at Sherlock Plumbing, Heating & Air, your San Diego area home comfort specialists with a team of sleuthing technicians ready to get to the bottom of your HVAC needs.