Where is the high limit switch located?

The high limit switch consists of a long temperature-sensing probe attached to a metal mounting plate. From the mounting plate, the switch is wired to the blower fan motor and to the gas valve. The switch is generally located just past the heat exchanger. This is so that it can detect the temperature of the supply air.

Where is the main limit switch on a furnace?

supply plenum
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.

How do you reset a high limit switch on a furnace?

How to Reset a Furnace Limit Switch

Locate your furnace’s heating duct.
Locate the white limit switch.
Look at each arm to identify the settings.
Identify the component (setting) located in between the two arms.
Set the temperature on the middle component to approximately 105 to 115 degrees Fahrenheit.

What causes high limit switch on furnace?

If the supply air is too hot, the interior of the furnace overheats, which can cause damage to components. The limit switch trips when temperatures are too hot, effectively shutting down the system and locking furnace operation until the unit cools.

How do you diagnose a bad limit switch?

The switch should be immediately suspect if the voltage drop is 0.2 VDC or higher (Fig. 1 indicates a bad limit switch). Verify that your ohmmeter will read “0” when the two leads are shorted together. The meter should read between “0” and “0.1” Ohms.

Can I bypass the limit switch on my furnace?

1 Answer. Yes, you can bypass the high limit switch for testing. It’s as trivial to do as it sounds.

Can you bypass a limit switch?

Can I bypass a high limit switch?

How long does it take for a limit switch to reset?

You can press the reset button up to three times before troubleshooting the furnace’s internal components or calling for repair service; allow 30 minutes between each reset. Consult your instruction manual before resetting your furnace’s limit switch.

Where is the high limit switch on a furnace?

It’s also safety device that helps prevent your furnace from overheating. The high limit switch consists of a long temperature-sensing probe attached to a metal mounting plate. From the mounting plate, the switch is wired to the blower fan motor and to the gas valve. The switch is generally located just past the heat exchanger.

Where is the high limit switch on a heat exchanger?

The switch is generally located just past the heat exchanger. This is so that it can detect the temperature of the supply air. In other words, the air that’s about to be blown into your home.

When does the high limit switch turn off?

The energy used to heat that air isn’t wasted. Sometimes the temperature of the supply air inside the furnace drops below a certain temperature. This is when the high limit switch signals the blower motor to turn off. The high limit switch is also an extremely important safety device inside your furnace.

How does the high limit switch work on a blower fan?

So the high limit switch detects the temperature of the supply air. When that air reaches a warm enough temperature, the switch tells the blower fan to come on. Ever notice there’s a two to three minute delay between when your thermostat switches the heat on and when the warm air actually comes out of the vents?

Where is the high limit switch on an electric furnace?

The furnace limit switch is generally found on the furnace just below the plenum. If the plenum reaches too high a temperature, the limit switch shuts it off.

How do you reset the limit switch on a furnace?

Press and hold the red “Reset” button in the center of the rollout limit switch component. Hold the button for one to two seconds before releasing it.

What is a high-temperature limit switch on a furnace?

A high-temperature limit switch, also called a fan limit switch or simply a limit switch, is an important device used in forced-air furnaces powered by gas or heating oil. Simply put, it senses the temperature of the furnace and tells the blower fan to turn on and off at the appropriate times.

Why is the limit switch on my furnace open?

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. On the left are some high temperature limits used in furnaces.