Can You Bypass the Furnace Limit Switch? Should You?


When it’s 20 degrees outside, the last thing you want is to wake up to a 50-degree house. A common method of furnace troubleshooting is to test the furnace limit switch, but can you bypass the furnace limit switch yourself? This article can help you decide whether or not to test your furnace yourself. 

The best option to avoid discontinuation of heat is to have your furnace routinely serviced. A trained HVAC technician can keep your furnace in good working order and prevent problems before they happen.

 Westerville’s furnace installation service team at World Class Services can provide the help you need when you need it. Call us at 614-532-4748 to connect with an expert!

What Is a Furnace Limit Switch?

The furnace limit switch is a small part of your furnace with a big job. If your furnace reaches a dangerous internal temperature, the limit switch will turn the furnace off. The limit switch keeps you and your family safe by preventing noxious gas from being released inside your home while reducing the risk of fire. 

If your furnace isn’t working properly, you may need a new limit switch. Fortunately, this is a common and inexpensive repair that you can do.

Can You Bypass the Furnace Limit Switch?

When your furnace malfunctions, it’s hard to stand back and wait for a professional. An easy way to test your furnace limit switch is to bypass it using jumper wires. 

So, can you bypass the furnace limit switch yourself?

The short answer is yes; bypassing the furnace limit switch yourself is possible. But before you grab your toolbox and run to the basement, there are some things you need to know to stay safe. 

Gather All Necessary Equipment

You only need a few things to bypass the furnace limit switch, such as:

  • Jumper wire
  • Pliers
  • Screwdriver (check your unit to determine if you need a Phillips head or flathead)

Once you have the necessary tools, you are ready to test your furnace limit switch.

Turn Off the Furnace

This should go without saying, but you can never be too careful. The furnace should never be on during cleaning or servicing.  Even if your furnace is not working, make sure to switch it off before opening the panel.

To go one step further, go to the breaker box and turn off the breaker to the furnace.

Keep it Short

You should not bypass your furnace limit switch for more than a few minutes to test it. The limit switch is a safety feature that keeps your gas furnace from climbing to a dangerous temperature. Though it may be tempting to do when you are freezing, don’t leave it open.

Follow these steps when testing the limit switch:

  • Using the screwdriver, remove the furnace access panel to reveal the limit switch.
  • Assess if the inside of your furnace needs cleaning. For the best result, let a professional do the cleaning.
  • Remove the wires attached to the limit switch.
  • Insert jumper wires into the limit switch.
  • Turn on the furnace.

If the furnace works while you have the jumper wires inserted, you need to replace your limit switch.

Should You Replace the Limit Switch Yourself?

Once you know you have a faulty limit switch on your hands, you can decide how to proceed. If you have experience in furnace repair, replacing it yourself is the cheapest option. The cost depends on your manufacturer, but a limit switch will generally cost around $20. 

Although it is possible to replace the limit switch yourself, the only way to guarantee a safe and effective replacement is by hiring experienced professionals.

Additionally, replacing your furnace limit switch can work for a while, but your unit may ultimately need replacement. Typically, if a furnace is more than 20 years old, you’ll benefit more from a whole-unit replacement.

Why Replace Your Furnace?

In 2022, President Biden proposed a new rule that would require new furnaces to have a 95% annual fuel utilization efficiency standard. In an attempt to keep up with the efforts to reduce natural gas consumption, this bill will phase out older machines in favor of newer models that are more environmentally friendly.

The good news is that newer furnace models cut down on natural resources and your monthly heating bill.

Keep Yourself Safe

Can you bypass the furnace limit switch yourself? Yes, but should you? We recommend getting expert help.

When it comes to an underperforming furnace, the most important thing is your safety. Call us at World Class Services in Westerville, Ohio, at 614-587-8985 to schedule furnace maintenance with a trained HVAC technician.

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