Tips for troubleshooting furnace problems yourself

Troubleshooting furnace problems requires extreme caution. While repairing a furnace is a job best left for professionals, you can do some basic investigation before calling a repairman. The days of simply relighting a pilot may be over for most people with modern furnaces, but the solution may not be as costly as you imagine.

Before you do anything, make sure to turn off the electric and gas to the HVAC system. Check the thermostat first, as this is the easiest component to assess. See that the thermostat and fan are both ON. A few things to look for:

– Thermostat is set too low
– Thermostat is broken

Potential Fixes:

– Move the thermostat to heat mode 
– Move the thermostat up or down and wait a minute to see if it?s working at all
– Clean thermostat if it is not digital. It?s possible the connectors are covered in dust.

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After checking the thermostat, move to the breaker, fuse and furnace switch:
– Is the circuit breaker powering the thermostat tripped or blown?

Potential Fixes:

– Before replacing the fuse, check to see if there is any loose wiring. Look for traces or burn spots on the fuse control board. If you find any, the furnace problem may be your control board. Hire a professional to make any necessary repairs to the control board and reset your furnace.
– Relight the pilot light
– If the breaker or fuse appears fine, your furnace problem may be the furnace control board, blower motor, run capacitor or the thermostat.

Next Steps for Troubleshooting your Furnace:

If your furnace has a condensed pump, make sure the reservoir is not full. The furnace is programmed to not run if the reservoir is full. Check the power and replace the pump. Once the blower motor is running again, turn the fan to automatic on the thermostat.

If your furnace runs on natural gas, check to see if the pilot light is out. Try relighting the pilot. Is the propane or natural gas valve closed?

What to look for if the furnace will not ignite:

– Potential problems may not be apparent to the untrained eye. It?s possible the igniter is cracked or the control board is not supplying voltage to the igniter

Possible Solution:

– You will most likely need to have a repairman install a new igniter

The furnace does not light and gas stays on for 10 seconds before shutting off:

Possible Solution:

– The flame sensor may need to be cleaned with sand paper or wool. Sometimes the flame sensor needs to be replaced, but it may just need a cleaning so it?s worth a try.

If your furnace produces a little heat, but not nearly enough to warm your home, your problem may be one of the following:

– Dirty furnace air filter
– Dirty gas burners

Possible Solutions:

– Replace air filter
– Have a professional clean the gas burners

If your furnace turns off and on frequently, your problem may be:

– Blower motor problem
– Thermostat is broken

Possible Solutions:

– Apply lightweight oil on the motor?s lubrication ports. Check belt suspension as this may need to be tightened or replaced.
– Adjust thermostat heat anticipator

Finish troubleshooting your furnace by observing a full heating cycle. When the burner shuts off, the fan should run for around 3 minutes. If the fan doesn?t shut off, it may be sticking and need to be replaced.

Once you?ve tried troubleshooting the HVAC system, it?s time to call a repairman. Ask what they charge for a visit and call around for the most affordable company. You can find online customer reviews for most furnace repair companies by doing a simple Google search for the company plus ?reviews?.

If it turns out that you need a new furnace, absolutely call around for estimates as prices can vary widely. The price may not seem like a bargain, but you?ll be glad you took care of your furnace problem before the peak season for repairmen arrives – especially when you can enjoy the first snowstorm from the warmth of your home.

References:
HVAC for Beginners: Troubleshooting
How Stuff Works: How to check your heating system