Most of the time a gas furnace runs reliably, especially if you keep it professionally serviced annually. In the rare event it doesn’t run as it should, these guidelines for troubleshooting a gas furnace might fix the problem safely and quickly before you need to reach for the phone.
Issue: Furnace Won’t Run
- Set the thermostat to “heat” and increase the heat a few degrees more than the current indoor temperature. If it doesn’t turn on shortly thereafter, clean the contacts inside the thermostat if it’s an older, non-digital model.
- Check the circuit breaker for the furnace or the switch inside the air handler. You may have to reset the system.
- The pilot light or electronic ignition system may be malfunctioning. Try relighting the pilot. If yours uses electronic ignition, you may need an HVAC expert to diagnose the problem.
Issue: Unusual Furnace Noises
- Rumbling or squeaking noises can signal a worn or loose belt, or the motor or blower assembly needs lubrication.
- Dirty burners often cause a rumbling sound, and they should be cleaned by a qualified HVAC technician.
- If you hear clanging or banging from the furnace during or just after it shuts off, contact an HVAC technician and turn the furnace off. It may signal a malfunction that could emit carbon monoxide into your home.
Issue: Inadequate Heat
- Check the air filter. If it’s completely blocked with dust, a safety switch inside the air handler may have turned the furnace off. Replace the air filter and check it monthly.
- The thermostat may also be at fault. Although thermostats look alike, they do differ in specific ways. If in doubt, contact an HVAC contractor to assess its compatibility. A bad thermostat can cycle the system on and off continuously, not giving your home time to heat.
- The fan setting at the thermostat could be set to “on.” When this is the case, it may seem like the furnace is blowing cold air after the combustion cycle is over. Switch the setting to “auto.”
If you need help troubleshooting a gas furnace, contact the pros at Griffith Energy Services. We’ve provided outstanding HVAC services for Baltimore area homeowners for more than 100 years.