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50+ Years of Serving
The Shreveport Area

50+ Years of Serving The Shreveport Area


Moon's Air Blog

6 Reasons Your Gas Furnace Isn’t Turning On


Here’s a frustration you don’t want to run into during the winter: the outdoor temperature has dropped, you’re shivering and so is everyone else in your house, so you set the thermostat to turn the furnace on… and nothing happens. Maybe the blower fan for the HVAC system activates, but the air coming from the vents is at room temperature. Or maybe there’s no air coming from the vents at all.

What has caused your gas furnace to give up? There are several possible reasons. Some you can troubleshoot, others will require that you call us for furnace repair in Bossier City, LA. We’ll look at six potential causes for furnace failure in more detail below.

1. Tripped breaker

Yes, your gas furnace needs to have electricity to run. The blower fan, for example, won’t come on if the HVAC system isn’t getting electrical current, and most gas furnaces use an electronic ignition system to light. A common reason for a furnace to fail to provide any action is because an overload has tripped the furnace’s circuit breaker. Check the house’s electrical panel and reset any tripped breakers to see if this fixes the problem. 

2. Clogged air filter

The air filter for the furnace can cause many difficulties if it’s left in place and becomes too dirty. (We recommend changing the filter every one to three months.) A clogged filter can cause the blower fan to overload its circuit. It can also lead to the heat exchanger in the furnace to overheat because not enough air is moving around it. An overheated exchanger will trip a limit switch and shut the furnace off. Change the filter to see if this gets the furnace back to work. 

3. Tripped flame rollout switch 

This is a safety mechanism that detects when flames from the burners escape from the furnace’s combustion chamber and to outside the furnace. This can happen because the flames aren’t getting enough oxygen and are billowing out to find other oxygen sources. If this switch trips, the furnace may not turn on again until the problem is repaired.

4. Lost connection with the thermostat

The problem may be due to the thermostat not sending any signals to the HVAC system’s control board. The furnace has to have instructions before it turns on, and if the thermostat has lost one of its connections, nothing will happen. Technicians can repair or replace the thermostat to fix this problem.

5. Failed ignition system

Furnaces built after 2010 use electronic ignitions systems to light the gas burners rather than a standing pilot light. The igniter can burn out, and when this happens the burners won’t light and a flame sensor will shut off gas flow as a safety measure. Technicians must replace a broken ignition system.

6. Gas flow problems

The burners may not be receiving any gas. This can happen because of blockage in the gas lines, a stuck valve, or even gas leaks. Please leave anything connected to the gas supply of your furnace to licensed professionals.

Moon’s Air has provided whole-home comfort since 1971. Call us for service today—it’s good to be Mooned!

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