High Limit Switch Furnace Troubleshooting

As a working example we examine the honeywell combination fan and limit control type l4064b.

High limit switch furnace troubleshooting.

As a safety the high limit switch turns the gas off when the temperature becomes too high. It also can shut down the furnace burners it if gets too hot inside the furnace. A clogged air filter restricts airflow through the heat exchanger causing the furnace to overheat. This article describes in detail the testing and diagnosis of problems with warm air heating furnace combination controls also commonly called the fan limit switch on warm air heating systems.

Clogged furnace filter a dirty or clogged filter blocks the air flow into the furnace which may raise the inside temperature of the unit. The limit switch is a safety switch that monitors t. Fan control limit switch. Next check the filter.

During your tune up not only will we inspect your limit switch but we will also take care of airflow issues with your system that can cause your limit switch to break down. Flip the switch on the side of your furnace and flip the breaker off and on again before you even think about replacing any parts. When the temperature gets too high the high limit switch turns off the gas to the furnace. Limit switches turn off the burner and turn on the circulating fan if there is a high temperature condition in the furnace.

If the furnace failure code indicates an open limit or open high temperature switch or open rollout switch it is probable that the furnace has overheated. How to check limit switches using your voltmeter. In this episode of repair and replace vance shows how to replace the high limit switch in a gas furnace. One way to keep your limit switch in good shape is to schedule a furnace tune up every year with jerry kelly.

The high temperature limit switch senses the temperature of a furnace and tells the blower fan to turn on and off at the appropriate times.