Gas Furnace Limit Switch Not Working

When your limit switch is not working correctly your furnace can overheat without shutting down as it should.

Gas furnace limit switch not working.

Mount and fasten access panels correctly. To troubleshoot a misbehaving gas furnace start with the easiest explanations and solutions then work your way to the most complicated. The limit switch includes a sensor in the heat exchanger to. However for your own safety don t attempt to reset the switch without first consulting your furnace s instruction manual.

A high limit control switch will turn off the gas to a furnace if the temperature becomes too high. It s possible to reset the switch at home when necessary by following a few simple steps. Belts sticking worn or damaged. Over time your furnace s limit switch can develop problems.

Spray squeaking drive belts with belt dressing. A limit switch also acts as a safety device for your furnace. 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. The flames would raise the temperature inside the unit and have no place to go getting hotter and hotter.

The gas fired forced air furnace fan limit switch in the photo below is pointed to by the red arrow. How to test and replace the fan limit switch on a furnace things to check before replacing the limit switch. Also a malfunctioning switch may not send signals to the air handler successfully which may cause the handler to never turn on. 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.

Furnace not working no gas flame. What happens if your furnace limit switch stops working properly. Reset limit switch for stop start cycling. Typically the lower pointer should be set to about 90.

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. 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. For example if the blower motor stopped running then no air would move through the unit. Limit control needs adjustment.

Limit switch set wrong. If the blower came on at the same time as the burner it would pump cold air through the house at first. 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.