Gas Furnace Limit Switch Not Working

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.

Gas furnace limit switch not working.

Also a malfunctioning switch may not send signals to the air handler successfully which may cause the handler to never turn on. How to test and replace the fan limit switch on a furnace things to check before replacing the limit switch. If the blower came on at the same time as the burner it would pump cold air through the house at first. The limit switch includes a sensor in the heat exchanger to.

Belts sticking worn or damaged. 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. Reset limit switch for stop start cycling.

Mount and fasten access panels correctly. 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. Replace worn or damaged belts. Limit switch set wrong.

Furnace not working no gas flame. The flames would raise the temperature inside the unit and have no place to go getting hotter and hotter. Limit control needs adjustment. According to honeywell voltage transients or even other conditions around the limit switch that impact the temperatures to which it is exposed can affect the cut on or cut off temperature behaviors of the switch but the company s instructions to not mention apparently excessive on off cycling of the furnace blower fan traced to the limit.

Spray squeaking drive belts with belt dressing. 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 gas fired forced air furnace fan limit switch in the photo below is pointed to by the red arrow. For example if the blower motor stopped running then no air would move through the unit.

What happens if your furnace limit switch stops working properly. 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. To troubleshoot a misbehaving gas furnace start with the easiest explanations and solutions then work your way to the most complicated. A limit switch also acts as a safety device for your furnace.

However for your own safety don t attempt to reset the switch without first consulting your furnace s instruction manual. Over time your furnace s limit switch can develop problems. Typically the lower pointer should be set to about 90.