What people keep running into with furnace repair
Complaints tagged furnace repair, each raised by more than one person. One-off posts are not included.
16 recurring problems · 275 people · 11 forums we read
Raised more than once
Most people first.
- 115Should I pay for appliance repair or fix it myself?Paying for professional service calls and OEM parts often costs hundreds of dollars more than buying third-party components online and fixing the appliance yourself. However, guessing wrong about whether a machine is actually safe to use can leave you with a dangerous hazard instead of a working fix.
- 46How to clear a clogged AC condensate drain lineAlgae and slime buildup inside condensate lines blocks airflow and water drainage, causing the drain pan to overflow and leak into ceilings or floors. Clearing the blockage requires snaking or pumping out the standing water in the PVC lines and U-joints to stop the immediate flooding.
- 18Should I replace old asbestos-wrapped ductwork while walls are open?When walls are open during renovations, deciding whether to replace old ductwork wrapped in asbestos depends on whether there is actual damage, though disturbing it raises safety and sizing concerns. Replacing the ducts can avoid future issues, but uncertainty about handling asbestos and potential sizing constraints with the existing unit makes homeowners hesitate to tear it out.
- 18Furnace lights up then immediately goes outEven after replacing the igniter, gas valve, and flame sensor, a furnace can fail to stay lit if the new igniter isn't drawing the correct amount of electrical current. This prevents the control board from sensing proper operation and keeping the gas valve open, stopping the system from completing its heating cycle.
- 16How to test a variable speed blower motor without expensive toolsDiagnosing a variable speed Genteq motor without an expensive $300 testing tool requires verifying that you are getting 240v line and 24v signals, and testing for 10 ohms between windings with no chassis continuity. If the fan clicks, restarts, and the wheel fails to spin freely like a bike tire, the motor may be failing due to a bad bearing. This often leaves people trying to figure out whether to replace just the end cap or buy an entire $500 motor.
- 14Why is my truck shaking and popping after replacing wheel hubs?Hearing a pop and feeling the truck shake right after replacing wheel hubs and bearings points to a sudden mechanical failure in the assembly, even when the axle nut is torqued to specification. The presence of metal shavings or "glitter" indicates internal component damage that prevents safe driving and requires immediate inspection.
- 9Why won't my water heater pilot light stay lit or spark?A lack of consistent spark forces people to hold the pilot button down until their fingers hurt while trying to light the unit. Because the pilot light ultimately won't stay lit, the system fails to ignite or operate.
- 8Why does my furnace make a loud banging noise?Delayed ignition causes a small explosion of built-up gas inside the combustion chamber, resulting in a loud bang when the furnace finally fires up. This issue stops the heating system from operating smoothly and requires immediate attention to prevent damage to the equipment during freezing weather.
- 7Why is my furnace blowing cold air with a red blinking light?A furnace blowing cold air and flashing a red error code often indicates a tripped pressure switch or an issue with the inducer motor preventing ignition. This stops the unit from heating your home, leaving you with unheated air running continuously. Fortunately, some underlying causes like blocked tubing can be checked and fixed at home.
- 5How to light the pilot light on an old furnaceOld furnaces often have hidden pilot assemblies or switches that fail to ignite even when following standard steps like holding the gas switch and hitting the igniter. This leaves homeowners struggling to figure out whether the system requires manual lighting or if there is a deeper mechanical failure, often forcing them to call a technician.
- 5Why does my thermostat keep losing power and resetting?A short in the 24V circuit or a failing HVAC transformer often causes the furnace control board to lose power, which trips the 3-amp safety device and kills the thermostat. This leaves the system completely dead or causes smart thermostats like the Nest and Ecobee to repeatedly reboot during a call for heat.
- 4Furnace won't turn on after new AC installationThe gas valve may have been left closed or something was missed during the recent HVAC installation, preventing the furnace from starting up when the weather turns cold. Homeowners worry that waiting too long to report the issue will make the warranty company or contractor upset about the delay.
- 3Why is my furnace inducer motor seized and hot?A seized furnace inducer motor prevents the system from starting while feeling hot to the touch. It can also emit a loud, high-pitched noise as it struggles to run.
- 3Why is water pooling inside my furnace?Water leaks in a furnace usually stem from internal issues like condensation drainage problems or components hidden behind the side or plastic panels. This unexpected pooling stops people from safely running their heating system without constant worry or hearing sloshing sounds from the fan.
- 2Furnace making a humming noise even when it is not runningA low-frequency hum or vibration coming from a furnace often traces back to an electrical issue or a stuck blower motor that is receiving power without spinning. While shutting off the furnace breaker stops the sound immediately, simply replacing components like the capacitor does not always resolve the underlying motor failure.
- 2New furnace short cycling every 10 minutesThe furnace runs for 8 to 10 minutes before shutting off, then restarts the burner about 30 seconds later. This short cycling persists even when bypassing the thermostat or completely removing the furnace doors and air filter to maximize return air.
Comes up alongside
Topics that keep appearing on the same problems — not topics with similar names.