Furnace Fan Limit Switch? Understanding This Common Heating Repair Issue

Most homeowners are careful to change filters and provide regular maintenance to help ensure that their home's furnace will remain reliable and efficient for the duration of each heating season. Like other major appliances, however, furnaces have many different mechanical and electrical components that can experience damage or wear capable of causing them to malfunction. Homeowners who have a good basic knowledge about some of the most common heating repair issues they are likely to face will be better positioned to deal with them and minimize the loss of comfort their family would likely experience. 

The furnace fan limit switch is an example of one such heating repair issue. Homeowners who want to learn more about furnace fan limit switches may find the following information to be helpful. 

When a fan limit switch malfunctions

As the name suggests, the function of a furnace fan limit switch is to create limitations on the operation of the fan. Furnace fan limit switches are designed to help ensure that the fan will not blow cold air by preventing it from operating until the heating cycle is sufficient to create properly warmed air. The fan limit switch also improves the efficiency of the furnace because it allows the fan to continue blowing after the heating cycle completes until the air temperature falls below the selected temperature. 

One of the most common signs that a furnace fan limit switch is malfunctioning is when the fan runs continuously, without shutting off between cycles. Fan limit switches that are failing may also cause electrical problems, such as tripped breakers in the home's electrical panel. 

Common reasons for fan limit switches to malfunction

As an electrical component, furnace fan limit switches can experience malfunction issues due to age and can also be damaged due to exposure to heat or moisture. In some instances, incorrect use of the home's thermostat can cause the fan limit switch to malfunction or experience excessive wear issues. To operate correctly, the fan limit switch must be able to detect the temperature inside the system's plenum. If the sensor used to detect this information has become dirty or damaged, the furnace fan limit switch may not signal the furnace to stop heating and may lead to overheating and more serious damage to the heating system. 

Homeowners who suspect that their furnace fan limit switch is beginning to malfunction will want to contact a reputable heating system repair contractor for immediate repairs to prevent a loss of heat or further damage to their furnace.