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The furnace fan limit switch is designed to activate and deactivate the furnace blower assembly. This component is responsible for transmitting warm air throughout the air ducts in your home. In addition, the furnace limit switch is also engineered to shut down the furnace to ensure it doesn’t overheat.
What is the main safety function of a fan limit switch?
While the primary function of the limit switch is to turn the blower fan on and off, it also has a safety role. When the temperature in the air supply plenum gets too hot, the limit switch turns off the furnace boiler to keep there from being any damage from overheating.
Where is the fan limit switch located?
Your fan limit switch is located inside the furnace panel cover, usually near the upper right corner. The fan limit switch is responsible for turning the blower on and off at the appropriate times.
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.
How much does a fan limit switch cost?
You will need to buy a high limit switch that is produced by the same manufacturer as your furnace unit. Depending on who your OEM is, this component could roughly cost you anywhere from $4 to $25.
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.
Can you clean a fan limit switch?
Remove the furnace access panel to locate the high limit switch on the outside of the plenum. Unscrew the switch from the plenum. Use steel wool or sandpaper to gently clean away soot and other materials stuck on the rod. Replace the switch and access panel.
How does a limit switch work 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. 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.
How do you bypass a fan limit switch?
How To Bypass the Furnace Limit Switch Locate the Limit Switch in the Furnace. Remove the two wires going to the Limit Switch. Insert a shielded jumper wire in-between the two wires. Once jumpered, test the furnace; if it works, the switch is bad and needs to be replaced.
Is it OK to run furnace fan constantly?
Running your furnace fan all the time isn’t exactly a bad thing. In fact, there’s no need to worry about the fan wearing out or breaking down because it’s designed to run continuously, and there’s an array of benefits connected to this.
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.
Should a limit switch be open or closed?
The limit switch is a normally closed switch in series with the sail switch and the thermostat. Being temperature actuated, it is designed to “snap open” when an over temperature condition occurs. Thus the switch is normally opening under full load conditions and that causes arcing of the contacts.
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.
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.
What is the purpose of a fan switch?
The switch on your fan reverses the direction of rotation on your fan. So it can spin clockwise or counter clockwise. Why would you want to change the direction of your fan? It can do a lot to make you more comfortable in both the warm summer and the cool winter.
What does a limit switch do on an actuator?
Limit switches use the mechanical movement of the actuator plunger to control or change the electrical switch’s state. Similar devices, such as inductive or capacitive proximity sensors, or photoelectric sensors, can accomplish the same result without requiring contact with the object.
Is it better to have furnace fan on auto or on?
Keeping your fan on AUTO is the most energy-efficient option. The fan only runs when the system is on and not continuously. If your fan runs continuously, moisture does not have a chance to drip outside. It blows back into your home and your AC works hard to remove extra moisture from the air.
