Gas Furnace Limit Switch Not Working

The gas fired forced air furnace fan limit switch in the photo below is pointed to by the red arrow.

Gas furnace limit switch not working. Belts sticking worn or damaged. Furnace not working no gas flame. Reset limit switch for stop start cycling. Call a furnace repair technician to adjust the limit switch or follow the instructions in your owner s manual to reset the pointers on the fan side of the limit control.

To troubleshoot a misbehaving gas furnace start with the easiest explanations and solutions then work your way to the most complicated. Limit control needs adjustment. The flames would raise the temperature inside the unit and have no place to go getting hotter and hotter. Mount and fasten access panels correctly.

A limit switch also acts as a safety device for your furnace. If it is set to off or auto the furnace s limit switch must be adjusted. Limit switch set wrong. The function of your furnace limit switch is to tell the fan when to turn off and on depending on the temperature in the home.

Spray squeaking drive belts with belt dressing. When your limit switch is not working correctly your furnace can overheat without shutting down as it should. It s possible to reset the switch at home when necessary by following a few simple steps. If the temperature inside of the plenum gets too hot it shuts off the gas supply to your burners to prevent your furnace and heat exchanger from overheating.

The limit switch includes a sensor in the heat exchanger to. If your gas furnace is blowing cold air a number of factors could be to blame many of which you can address on your own without the immediate help of a service professional. However for your own safety don t attempt to reset the switch without first consulting your furnace s instruction manual. What happens if your furnace limit switch stops working properly.

If the blower came on at the same time as the burner it would pump cold air through the house at first. How to test and replace the fan limit switch on a furnace things to check before replacing the limit switch. Replace worn or damaged belts. A high limit control switch will turn off the gas to a furnace if the temperature becomes too high.

Also a malfunctioning switch may not send signals to the air handler successfully which may cause the handler to never turn on. Over time your furnace s limit switch can develop problems. For example if the blower motor stopped running then no air would move through the unit.