What causes a furnace limit switch to trip?

The limit might trip after start-up due to a restrictive or dirty air filter. Some high performance air filters do not allow very much airflow through them and will cause a furnace to overheat due to a lack of air going across the heat exchanger. Another reason could be a bypass humidifier.

Why does my high limit switch keep tripping?

The Limit Switch Needs Replacement Over time, high limit switches can wear out and weaken. A faulty high limit switch can trip at lower temperatures, causing short cycling and triggering lockout mode even though the furnace is not actually overheating.

How do I know if my fan limit switch is bad?

The most common sign of a malfunctioning limit switch is the continuous operation of your furnace’s blower. Just as the limit switch won’t allow the fan to turn on until the warm air has reached the right temperature, the limit switch also shuts down when the air cools to a certain temperature.

Can you reset a fan limit switch?

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. However, for your own safety, don’t attempt to reset the switch without first consulting your furnace’s instruction manual.

What causes a limit switch to open?

Limit switch codes The limit switch shuts off the burner when the temperature exceeds a preset temperature. When the temperature reduces to normal, the burner will come back on. The most common reason for limits to open is a plugged filter or a dirty blower wheel.

Can a furnace high limit switch go bad?

Like any other part in your HVAC system, the high limit switch can wear out over time. One of the most common issues that happens when a high limit switch goes bad is that it fails to signal the blower fan to turn off. High limit switches can also weaken over time so that they begin tripping at a lower temperature.

How much does it cost to replace a limit switch on a furnace?

Average Cost of a New Furnace Limit Switch Depending on who your OEM is, this component could roughly cost you anywhere from $4 to $25.

What are the causes when a limit switch opens?

Limit switch codes Limit switches turn off the burner and turn on the circulating fan if there is a high temperature condition in the furnace. When the temperature reduces to normal, the burner will come back on. The most common reason for limits to open is a plugged filter or a dirty blower wheel.