To reset a furnace limit switch, turn off power at the breaker, remove the furnace control panel, and hold the reset button for about three seconds. If your furnace keeps shutting itself down, the limit switch is often the reason, and it is usually reacting to a real airflow problem. As a veteran-owned, family-operated team with NATE and EPA-certified technicians, Leith Heating and Cooling helps Elgin homeowners get to the bottom of it. When a reset does not stick, we handle furnace repair in Elgin, IL with upfront pricing.
Key Points
- To reset a furnace limit switch, cut power at the breaker, remove the control panel, and hold the reset button for three seconds.
- The limit switch is a safety control that shuts your furnace down before it overheats.
- A switch that keeps tripping usually points to airflow problems like a clogged filter, closed vents, or dirty coils.
- If resets do not hold, a worn-out switch or faulty blower motor may need professional attention.
Why Does Your Furnace Limit Switch Keep Tripping?
A limit switch trips when your furnace runs hotter than it should, and airflow problems are the most common cause. Resetting the limit switch on a furnace is a method you can use to investigate furnace malfunction issues. During operation, your limit switch may activate its furnace overheat protection reset. If there is something faulty going on with your furnace, some limit switch troubleshooting methods may help you find the cause.
Learning how to reset a limit switch on a furnace starts with understanding the potential causes of overheating, which include the following.
Clogged Air Filters
When air filters become clogged with dirt and dust, this creates a heat bottleneck that can trick your limit switch into thinking things are hotter than they actually are. Since heat activates the limit switch in an effort to prevent your unit from overheating, a clogged air filter may cause your limit switch to continuously send out false signals. Regular furnace maintenance in Elgin, IL keeps filters, coils, and airflow in check before they trip your limit switch.
Overactive Cycles
As the blower motor sends hot air from the coils into your home, a limit switch may trigger because it senses either too hot or too cold of conditions within the vents, causing a shortened cycle. Short cycles are self-imposing, making the limit switch work against the furnace instead of for it. If you believe your limit switch is simply reacting to a short cycle in temperature, resetting the limit switch on your furnace may fix the problem.
High Heat
One of the simplest ways to activate a limit switch is by introducing excessive heat to your furnace system. Whether due to a clogged vent or dirty filter, heat causes a limit switch to activate to keep your furnace and house safe.
You can expect repeated tripping if your furnace overheats easily due to a lack of maintenance. If you need to keep resetting your furnace for the sake of its interior temperature, odds are something is clogging the way for heat to escape.
Closed Vents
If your vent is closed or blocked, heat cannot properly flow from the blowers to the rest of your home. Having too many closed vents in your air circulation system can suffocate your furnace and keep things hot enough to trip your limit switch.
If opening your vents and ensuring your airways are clear solves the issue, then you will not need to rely on a limit switch reset to get your furnace back in order.
Faulty Blower Motor
If your furnace is doing nothing but heating without blowing all that hot air into your home, it could cause problems for your limit switch. A faulty blower motor may be blowing air out from your vents, but if it is not doing this fast enough, hot air could accumulate throughout the entire system, tripping your limit switch.
Dirty Coils
Just the same as other heat-accumulating problems that a furnace can create, dirty coils can be responsible for false alarms. A coil covered in debris or dust can overheat the entire furnace.
If you notice excessive heat, the best thing to do is clean everything, from your filter to the coils. However, this is a job best left to professionals who have the right equipment and knowledge.
A Broken Limit Switch
If you have determined that none of the above issues exist within your furnace, odds are your limit switch is the ongoing problem. Limit switches that continuously trip without explanation are likely worn out due to age or continuous heat exposure. A trusted furnace company in Elgin, IL can test the switch and replace it if needed.
How Do You Reset a Furnace Limit Switch?
You reset a furnace limit switch in three steps: cut the power, open the control panel, and hold the reset button. Here is how to do it safely:
1. Turn off Your Furnace
When dealing with a furnace issue, you should always deactivate the power first. You can do this by going to your circuit breaker and turning off the switch for your heating system. Ensuring the power is out on your heater can help prevent accidents as you troubleshoot your issues.
2. Check the Control Panel
Once you have powered down everything, locate your control panel and lift it off the furnace. Depending on your furnace, there should be handles on each side that can make this easier. After removing it, set the control panel aside so that you can focus on the interior.
3. Locate Your Furnace Limit Switch
To find the limit switch on your furnace, look for a red, yellow, or white button on the panel. To restart your furnace manually, hold this button for three seconds before releasing it. After restarting the system, affix your control panel back on the furnace and turn your furnace back on via the circuit breaker.
Frequently Asked Questions
Where is the limit switch on a furnace?
The limit switch sits behind your furnace’s control panel, and it usually looks like a red, yellow, or white button. Turn off power at the breaker, lift the panel off, and you will find it inside. Hold the button for three seconds to reset it.
Why does my furnace limit switch keep tripping after a reset?
A limit switch that keeps tripping is almost always reacting to trapped heat. Clogged filters, closed vents, dirty coils, or a slow blower motor are the usual suspects. If none of those apply, the switch itself may be worn out from age or continuous heat exposure.
Is it safe to keep resetting a furnace limit switch?
No, repeated resets are a warning sign, not a fix. The switch exists to keep your furnace from reaching dangerous temperatures, so constant tripping means heat is not escaping the way it should. Find and fix the airflow problem, or have a professional take a look.
Need Help With Your Furnace Limit Switch in Elgin, IL?
Now that you understand how to reset a limit switch on a furnace, have you narrowed down what your furnace problem might be? For issues like flame detection rod cleanings and limit switch adjustments, a professional may need to step in. If your furnace is aging and repeated overheating keeps wearing out components, it may be time to ask about furnace installation in Elgin, IL.
If you need to keep resetting your furnace or have other heating issues, contact our team today. Our experts in Elgin, Illinois, are happy to help, so call 847-565-1538.