How To Test Furnace Limit Switch With Multimeter?

How to Test a Furnace Limit Switch with a Multimeter

Your furnace limit switch is a safety device that prevents your furnace from overheating. It does this by shutting off the furnace when the temperature reaches a certain level. If your furnace limit switch is not working properly, it could allow your furnace to overheat, which could be dangerous.

Testing your furnace limit switch with a multimeter is a relatively simple task that you can do yourself. By following the steps in this guide, you can quickly and easily determine if your limit switch is working properly.

What is a Furnace Limit Switch?

A furnace limit switch is a safety device that is used to prevent your furnace from overheating. It does this by shutting off the furnace when the temperature reaches a certain level. The limit switch is typically located on the furnace blower housing.

Furnace limit switches are typically either bimetallic or electronic. Bimetallic limit switches use two metal strips that are joined together. When the temperature rises, the metal strips expand at different rates. This causes the strips to bend, which eventually triggers the limit switch to shut off the furnace.

Electronic limit switches use a sensor to detect the temperature. When the temperature reaches a certain level, the sensor sends a signal to the limit switch, which shuts off the furnace.

How to Test a Furnace Limit Switch with a Multimeter

To test a furnace limit switch with a multimeter, you will need the following tools:

• A multimeter
• A set of insulated pliers
• A screwdriver

Step 1: Turn off the power to the furnace.

The first step is to turn off the power to the furnace. This will prevent you from getting shocked.

Step 2: Locate the limit switch.

The limit switch is typically located on the furnace blower housing. It is a small, rectangular device with two terminals.

Step 3: Set the multimeter to ohms.

The next step is to set your multimeter to ohms. This will allow you to test the continuity of the limit switch.

Step 4: Touch the multimeter probes to the terminals of the limit switch.

Once the multimeter is set to ohms, touch the red probe to one terminal of the limit switch and the black probe to the other terminal.

Step 5: Observe the multimeter display.

If the limit switch is working properly, the multimeter display should show a reading of zero ohms. This indicates that there is continuity between the two terminals of the limit switch.

Step 6: Turn on the power to the furnace.

Once you have confirmed that the limit switch is working properly, you can turn on the power to the furnace.

Step	Action	Explanation
1	Turn off the power to the furnace.	This will prevent you from getting shocked.
2	Locate the limit switch.	It is usually located near the furnace’s heat exchanger.
3	Set your multimeter to the resistance setting.	This will allow you to measure the resistance of the switch.
4	Touch the multimeter’s probes to the terminals of the limit switch.	One probe should be connected to the “hot” terminal and the other probe should be connected to the “common” terminal.
5	Check the multimeter’s display.	If the display shows a reading of “0” ohms, the switch is closed and functioning properly.
6	If the display shows a reading of “infinity” ohms, the switch is open and not functioning properly.	You will need to replace the limit switch.

What is a Furnace Limit Switch?

A furnace limit switch is a safety device that prevents your furnace from overheating. It does this by turning off the furnace when the temperature inside the furnace reaches a certain level. This prevents the furnace from causing a fire or other damage.

Furnace limit switches are typically located on the side of the furnace, near the heat exchanger. They are usually round or rectangular, and they have two terminals.

There are two types of furnace limit switches: high limit switches and low limit switches. High limit switches turn off the furnace when the temperature inside the furnace gets too high. Low limit switches turn off the furnace when the temperature inside the furnace gets too low.

Furnace limit switches are an important safety device. They help to prevent fires and other damage by preventing the furnace from overheating or from getting too cold.

How to Test a Furnace Limit Switch with a Multimeter

To test a furnace limit switch with a multimeter, you will need the following:

• A multimeter
• A set of test leads
• Safety glasses

Step 1: Turn off the power to the furnace.

Before you start testing the furnace limit switch, you need to turn off the power to the furnace. This will prevent you from getting shocked.

Step 2: Locate the furnace limit switch.

The furnace limit switch is typically located on the side of the furnace, near the heat exchanger. It is usually round or rectangular, and it has two terminals.

Step 3: Set the multimeter to ohms.

The multimeter should be set to the ohms setting.

Step 4: Connect the test leads to the multimeter.

One test lead should be connected to the “COM” terminal on the multimeter. The other test lead should be connected to the “V” terminal on the multimeter.

Step 5: Test the high limit switch.

To test the high limit switch, disconnect the wires from the switch. Then, connect the red test lead to the “hot” terminal on the switch. Connect the black test lead to the “common” terminal on the switch.

The multimeter should read “0 ohms”. If the multimeter does not read “0 ohms”, the high limit switch is bad and needs to be replaced.

Step 6: Test the low limit switch.

To test the low limit switch, reconnect the wires to the switch. Then, connect the red test lead to the “common” terminal on the switch. Connect the black test lead to the “hot” terminal on the switch.

The multimeter should read “0 ohms”. If the multimeter does not read “0 ohms”, the low limit switch is bad and needs to be replaced.

Step 7: Turn on the power to the furnace.

Once you have finished testing the furnace limit switch, turn on the power to the furnace.

Testing a furnace limit switch with a multimeter is a simple process. By following the steps in this guide, you can quickly and easily determine if the furnace limit switch is working properly.

If you find that the furnace limit switch is bad, you will need to replace it. You can find furnace limit switches at most home improvement stores.

How to Test Furnace Limit Switch With Multimeter?

A furnace limit switch is a safety device that prevents your furnace from overheating. It does this by turning off the furnace when the temperature reaches a certain point. If your furnace limit switch is not working properly, it can cause your furnace to overheat and damage itself.

You can test your furnace limit switch with a multimeter to see if it is working properly. Here are the steps:

1. Turn off the power to your furnace.
2. Disconnect the wires from the limit switch.
3. Set your multimeter to the ohms setting.
4. Touch one probe of the multimeter to the common terminal on the limit switch.
5. Touch the other probe of the multimeter to the normally open terminal on the limit switch.
6. The multimeter should read infinity.
7. Reconnect the wires to the limit switch.
8. Turn on the power to your furnace.

If the multimeter reads infinity, the limit switch is working properly. If the multimeter reads anything other than infinity, the limit switch is bad and needs to be replaced.

Common problems with furnace limit switches

There are a few common problems that can occur with furnace limit switches. These include:

• The limit switch is stuck open. This means that the switch is not turning off the furnace when the temperature reaches a certain point. This can cause your furnace to overheat and damage itself.
• The limit switch is stuck closed. This means that the switch is not turning on the furnace when the temperature drops below a certain point. This can cause your furnace to not work properly when it is cold outside.
• The limit switch is damaged. This can happen if the switch is exposed to too much heat or if it is struck by something. A damaged limit switch will not work properly and will need to be replaced.

If you think that your furnace limit switch is not working properly, you should have it checked by a qualified technician.

How to replace a furnace limit switch

Replacing a furnace limit switch is a relatively simple task that can be completed by most homeowners. Here are the steps involved:

1. Turn off the power to your furnace.
2. Disconnect the wires from the old limit switch.
3. Remove the old limit switch from the furnace.
4. Install the new limit switch in the furnace.
5. Reconnect the wires to the new limit switch.
6. Turn on the power to your furnace.

Here are some additional tips for replacing a furnace limit switch:

• Make sure that the new limit switch is the same type as the old limit switch.
• Be careful not to damage the wires when you are disconnecting them from the old limit switch.
• Make sure that the new limit switch is installed correctly.
• Test the new limit switch to make sure that it is working properly.

If you are not comfortable replacing a furnace limit switch, you should have it done by a qualified technician.

Furnace limit switches are an important safety device that prevents your furnace from overheating. If you think that your furnace limit switch is not working properly, you should have it checked by a qualified technician.

How do I test a furnace limit switch with a multimeter?

1. Turn off the power to the furnace. This is a safety precaution to prevent you from getting shocked.
2. Locate the limit switch. The limit switch is usually located on the furnace’s heat exchanger. It is a small, cylindrical device with two terminals.
3. Set your multimeter to the resistance setting. The resistance setting is usually the ohms symbol ().
4. Touch the red probe of the multimeter to one terminal of the limit switch.
5. Touch the black probe of the multimeter to the other terminal of the limit switch.
6. The multimeter should display a reading of zero ohms. If the multimeter displays a reading of infinity ohms, the limit switch is bad and needs to be replaced.

What are the symptoms of a bad limit switch?

• The furnace will not turn on.
• The furnace will turn on but will not stay on.
• The furnace will turn on but will not heat the house.
• The furnace will overheat and shut down.

How do I replace a furnace limit switch?

1. Turn off the power to the furnace.
2. Locate the limit switch. The limit switch is usually located on the furnace’s heat exchanger. It is a small, cylindrical device with two terminals.
3. Remove the screws that hold the limit switch in place.
4. Disconnect the wires from the limit switch.
5. Install the new limit switch.
6. Reconnect the wires to the limit switch.
7. Secure the limit switch with the screws.
8. Turn on the power to the furnace.

What is the difference between a high limit switch and a low limit switch?

A high limit switch is a safety device that prevents the furnace from overheating. It is usually set to a temperature of 195 degrees Fahrenheit. A low limit switch is a safety device that prevents the furnace from freezing. It is usually set to a temperature of 55 degrees Fahrenheit.

How often should I test my furnace limit switch?

It is a good idea to test your furnace limit switch every year. This will help to ensure that your furnace is operating properly and that you are not at risk of a fire or carbon monoxide poisoning.

testing your furnace limit switch with a multimeter is a simple and straightforward process that can help you identify any potential problems. By following the steps outlined in this guide, you can quickly and easily ensure that your furnace is operating safely and efficiently.

Here are some key takeaways from this guide:

• The furnace limit switch is a safety device that prevents your furnace from overheating.
• The limit switch is located on the furnace control board.
• You can test the limit switch with a multimeter by setting the multimeter to the ohms setting and connecting the leads to the terminals on the switch.
• If the multimeter reads OL, the limit switch is open and needs to be replaced.
• If the multimeter reads 0 ohms, the limit switch is closed and is working properly.

By following these steps, you can help keep your furnace running safely and efficiently for years to come.