Furnace Troubleshooting: 5 Problems You Can Fix Yourself
Furnace Troubleshooting: 5 Problems You Can Fix Yourself
Your furnace stops working, your home is getting cold, and you’re dreading an expensive emergency service call. Before you pick up the phone, try these five troubleshooting steps that resolve the majority of common furnace problems — many of which cost nothing to fix. According to the U.S. Department of Energy (energy.gov), simple issues like dirty filters, tripped breakers, and thermostat settings account for approximately 40% of no-heat service calls.
Problem 1: Thermostat Issues. Check that the thermostat is set to HEAT mode (not cool, off, or auto). Verify the setpoint is above the current room temperature. Replace the batteries if applicable. Try setting the temperature 5 degrees above room temperature and wait 5 minutes. If the thermostat screen is blank, check the batteries and breaker.
Problem 2: Dirty Air Filter. A severely clogged filter restricts airflow enough to trigger the high-limit safety switch, shutting down the furnace. Pull the filter and inspect it. If it’s completely blocked, replace it immediately. Wait 30 minutes after replacing the filter for the high-limit switch to reset, then try restarting the furnace.
Problem 3: Tripped Circuit Breaker. Check your electrical panel for the breaker labeled Furnace or Air Handler. If it’s tripped (in the middle position), flip it fully OFF, wait 30 seconds, then flip it to ON. If the breaker trips again immediately, there’s an electrical fault — call a professional.
Problem 4: Blocked Condensate Drain. High-efficiency furnaces (90%+ AFUE) produce condensation that drains through a tube. If this tube clogs (common with algae and sediment), the furnace shuts down to prevent overflow. Check the condensate drain line and clear any visible blockage. Flush with distilled white vinegar.
Problem 5: Pilot Light or Igniter Issues. For standing pilot systems (older furnaces), check if the pilot is lit. Follow the manufacturer’s instructions on the furnace panel to relight. For electronic ignition systems, listen for clicking sounds (indicating the igniter is trying to fire). If you hear clicking but no ignition, the igniter may need cleaning or replacement — this requires professional service.
When to Call a Professional
If you’ve tried the above and the furnace still doesn’t work, it’s time for professional help. Also call immediately if you smell gas (evacuate first, call 911, then call your utility), the furnace makes unusual loud noises, the CO detector is alarming, or there’s water pooling around the furnace.
Frequently Asked Questions
Why does my furnace keep shutting off after a few seconds?
The most common cause is a dirty flame sensor — a small metal rod that detects the burner flame. When coated with oxide, it can’t sense the flame and shuts off the gas valve. A professional cleaning ($80-150) fixes this quickly.
How often should I change my furnace filter?
Every 1-3 months during heating season, depending on the filter type. 1-inch filters need monthly replacement. 4-inch media filters last 3-6 months. Check monthly and replace when visibly dirty.
Does JDL offer furnace repair?
Yes — JDL HVAC & Plumbing Services provides same-day furnace repair throughout the DMV. If your DIY troubleshooting doesn’t resolve the issue, call (844) 535-4822 for professional diagnosis and repair.
Serving the Greater DMV Area
JDL HVAC & Plumbing Services proudly serves homeowners across Maryland, Virginia, and Washington D.C.
Maryland: Laurel | Bowie | Crofton | Upper Marlboro | Columbia | Annapolis | Odenton | Severn | Glen Burnie
Virginia: Northern Virginia | DC: Washington, DC
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