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A furnace limit switch is a component of a forced-air furnace that is responsible for turning on the furnace blower once the desired heat has been met inside the furnace. Without a functioning furnace limit switch, a furnace would not be able to regulate the temperature in conjunction with a thermostat.
How do you know if a 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.
What causes a furnace limit switch to trip?
If the air inside your furnace gets too hot, the limit switch trips to prevent overheating. If the furnace high limit switch trips due to overheating, there is likely an airflow issue that is preventing proper air movement through the system. A dirty filter is the most common cause of airflow issues.
Can you bypass furnace limit switch?
When testing if a switch is good or bad, it can be bypassed for a short time. This is a common method to see if the switch needs a replacement. The limit switch turns the furnace off when it becomes too hot, which prevents the heat exchanger from becoming damaged.
How do you reset a limit switch on a furnace?
How to Reset Furnace Limit Switch. Once the problem affecting your furnace has been identified and corrected, you should reset your furnace to continue enjoying the warmth on your home. In most gas furnace, this is done by simply shutting off the power supply and turning it back on after 20 or so seconds.
How much does it cost to replace a limit switch?
You’ll need to get a limit switch from the same company that makes your furnace. This component could cost anywhere from $4 to $25, depending on your original equipment manufacturer.
Can you reset a 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.
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 does a tripped limit switch look like?
The most common way to tell if a limit switch is tripped is to observe the behavior of your furnace: Your furnace’s heating cycles end right after they begin. If the furnace won’t ignite, but the blower fan stays running, then the high limit switch might be tripped.
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.
Are furnace limit switches normally open?
The fan limit switch is normally open and closes when the temperature reaches its preset value, whereas the high limit switch is normally closed and opens when the temperature reaches its threshold value.
What is a limit switch?
A limit switch is an electromechanical device operated by a physical force applied to it by an object. Limit switches are used to detect the presence or absence of an object. These switches were originally used to define the limit of travel of an object, and as a result, they were named Limit Switch.
Is my furnace limit switch bad?
One common symptom of a malfunctioning limit switch is a blower fan that doesn’t shut off. A bad switch also can prevent a furnace from operating at all. If the switch has completely failed and is stuck in the open circuit (off) position, the furnace won’t run.
What will cause 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.
Where is a limit switch on a furnace?
A limit switch is a device that’s located under your furnace’s supply plenum. It reads the temperature of the plenum and waits until it gets appropriately warm. Once the plenum reaches a specific temperature, the limit switch sends a signal to the air handler to begin running and delivering warm air to your home.
Can you run a furnace without a limit switch?
Without a functioning furnace limit switch, a furnace would not be able to regulate the temperature in conjunction with a thermostat. Typically, a furnace limit switch consists of an exterior plate and a temperature probe that lives inside the furnace housing.
Why does my furnace limit switch keep tripping?
A high limit switch will keep tripping due to a dirty flame sensor, short cycling, obstructed airflow, or a defective switch. These lead to overheating within the gas furnace that triggers tripping as a safety measure to prevent fires. Clean and replace dirty and worn-out parts to fix the problem.
