What is a Limit Switch on a Furnace?

The limit switch tells your furnace when to turn off and on and prevents your heat exchange from overheating.

If your furnace doesn’t turn on, a limit switch malfunction may be to blame.

Below you’ll find everything you need to know about limit switches and how much it costs to replace one.

Let’s get started.

What is a Limit Switch on a Furnace?

The furnace limit switch turns on your furnace blower once your furnace has been brought up to your desired temperature.

The limit switch is also responsible for turning off your furnace should the temperature inside get too high.

Limit switches are used in natural gas, oil, and propane furnaces.

How Your Limit Switch Makes Your Furnace Safe

Your furnace is a complex machine that relies on many different parts to operate properly.

Once the thermostat is set to a certain temperature, the burners will ignite and start to heat the heat exchanger.

Your limit switch will keep the blower off until the temperature inside of your furnace meets the temperature that your thermostat is set to.

Once it senses the desired temperature, your limit switch will turn on your blower fan so the warm air can get to the rooms in your home.

Once the thermostat senses your home is at the desired temperature, it will tell your furnace to shut off the burners.

The limit switch will continue running the blower fan removing as much heat from the heat exchanger as possible.

Once the air temperature inside of the furnace reaches the lower limit, it will then continue the cycle again.

Your limit switch will also turn off your burners if it senses the heat exchanger is getting too hot.

If your heat exchanger is damaged by overheating, it can cause cracking and lead to carbon monoxide leaks.

Heat exchangers are costly repairs and can cost anywhere from $2000 to $3500 depending on where you live and the type of furnace you have.

Signs Your Limit Switch is Failing

Blower fan doesn’t shut off

A telltale sign that you have a malfunctioning limit switch is that the blower fan runs nonstop.

If your limit switch is broken, it will be unable to sense the temperatures and operate the blower fan like normal.

Furnace doesn’t turn on

Another telltale sign the limit switch is broken is if your furnace doesn’t operate at all.

If the limit switch has failed, it will be stuck in an open position and will not allow your furnace to turn on.

This is similar to the protection mechanism when your furnace overheats.

Reasons Your Limit Switch is Tripped

Your limit switch can be tripped if it gets dirty which can happen after years of usage.

A dirty furnace filter or improperly installed furnace filter can also causereduced airflow, and trip your limit switch from overheating.

Is a Limit Switch the same as a Pressure Switch?

The pressure switch is located on the outside of your furnace while the limit switch is on the inside.

The pressure switch detects negative pressure inside of your furnace and will shut the furnace down if it does sense negative pressure.

Your limit switch senses the temperature inside of your furnace and turns your furnace off and on and is used to prevent overheating.

Can You Replace Your Own High Temperature Limit Switch?

If you know how to use a multi meter and understand electronic components, then you should be able to fix your own limit switch.

If you are apprehensive about doing any repairs, then it’s best to rely on a certified HVAC technician that can replace your furnace limit switch.

How Much Does it Cost to Replace a Furnace Limit Switch?

A furnace limit switch can cost anywhere from $5 to $25 for the replacement part.

You should expect to pay anywhere from $100 to $1000 depending on what the actual problem is after furnace diagnostics take place.

When to Call a Service Professional?

You should call an HVAC professional service if you don’t know how to replace the limit switch on your own.

Remember that a forced-air heating system is a complex machine that deals with heat, and you don’t want to put yourself or your family in danger.

To get in touch with certified HVAC technicians, click the button below and you’ll be given a free quote in a matter of minutes.

Never repair a furnace on your own if you don’t understand what you’re doing as you may put yourself at risk.

About Roy Cohen

Roy Cohen has a burning passion for heating, cooling, and ventilation. He aims to help you save money on expensive repairs and bring you the best HVAC products. He has years of experience behind him in HVAC repair and garage maintenance.

You can find Roy at his LinkedIn or his email: [email protected]

Related Posts