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Kilowatt Heating, Air Conditioning and Electrical Blog

Why Does My Gas Furnace Keep Shutting Off?


We’re going through what will probably be the coldest weather of the season here in Southern California. That might seem warm to people on the East Coast, but it’s definitely cold enough that we’ll need our heating systems running. This is the point when you’re most likely to find out if your heating system is up to its job. If you have heating maintenance done at the start of winter, you can expect to run into few problems. But even the best maintenance can’t prevent all malfunctions. 

For instance, you may discover that your gas furnace isn’t running long enough to warm up the house, either shutting off after a few minutes or shutting off almost right away. What’s the cause of this? There are several possible sources, which we’ll look at below.

Faulty flame sensor

We wrote about the flame sensor in a recent post: it’s a safety mechanism that shuts off the gas to the burners if the burners fail to ignite. But if the flame sensor is faulty or dirty, it may shut the gas off no matter what, and the gas flames will go out. You can call technicians to take care of the repair necessary to fix the flame sensor.

Reduced airflow

The furnace needs a proper level of airflow through it, not only to ensure enough air is heated and then distributed to the rooms, but also to cool down the heat exchanger. Without sufficient airflow, the heat exchanger will remain too hot, and this will trigger a limit switch to shut down the furnace. The lack of airflow may be due to a clogged furnace filter, which you can change on your own. It might also be due to problems with the blower motor, and this requires professionals to fix. 

Miscalibrated or faulty thermostat

The thermostat may be shutting off your furnace too early because it’s signaling to the furnace that it’s completed a heating cycle when it hasn’t. This is often due to the thermostat becoming miscalibrated by more than 5° so that it senses the house is warmer than it is. There are other ways a thermostat can send incorrect instructions to the HVAC systems. Our technicians can recalibrate the thermostat, or repair or replace it as necessary. 

Gas flow problems

The burners may not be receiving enough gas, so the furnace shuts off early. This can be due to blockage in the gas line or a stuck gas valve. Please don’t try to investigate gas troubles on your own—stay safe and let professionals check on the problem.

Dirty burners

If the gas burner becomes too covered in grime or carbon build-up, it won’t be able to draw on enough oxygen to stay lit for long. HVAC technicians will need to detach the burner to properly clean it so it can function again.

Overheated motors

The blower motor draws on a large amount of electricity to run, so if the motor overheats or has a short, it may cause the circuit breaker to the furnace to trip, shutting down the entire furnace. The motor probably needs to be replaced. Don’t attempt to keep turning on the furnace if it’s tripping the breaker.

Reach out to us for any heating repair in Lake Balboa, CA you need.

Call our certified service technicians 24/7 for exceptional customer service! Kilowatt Heating, Air Conditioning and Electrical serves Los Angeles and the San Fernando Valley.

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