AC Thermostat Keeps Resetting To 85—What To Do?

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Sometimes you may not know there’s a thermostat resetting until you suddenly feel that your home has grown much warmer. If your thermostat keeps rising to 85 degrees Fahrenheit, there’s likely an issue with the unit that you should investigate. We have researched the most common reasons for this, and we will go over them in this post.

Here are a few reasons why your thermostat may keep resetting to 85 degrees:

  • You have the thermostat programmed to 85 degrees
  • The batteries need replacement 
  • The thermostat has a blown fuse
  • The thermostat has wiring issues

Sometimes a thermostat that keeps resetting can be fixed in a matter of minutes. Other times, the issue may be so complex that it requires assistance from an experienced HVAC technician. Continue reading to learn the various scenarios that may cause this issue and when it’s time to call out the pros.

A man adjusting the thermostat, AC Thermostat Keeps Resetting To 85—What To Do?

 

Potential Reasons Why Your Thermostat Keeps Resetting to 85

You Have the Thermostat Programmed to 85 Degrees

Sometimes, a brand new thermostat may have a factory setting that is at a specific temperature. And there are times when another member of your household made program it without your knowledge. Lastly, if you’ve recently moved into a new house, the thermostat may already be programmed to 85°.

If it keeps rising to a specific temperature, always check the thermostat setting to determine if this is the culprit of the constant resetting. If it is, pull out your manual to learn how to reset it to the temperature that you prefer.

The Batteries Need Replacement

If you have a non-programmable thermostat, the problem could be that the batteries are old and need changing. It’s common to think that you recently changed the batteries to the thermostat, but sometimes the change date is older than you realize—and not all thermostats have a display that shows when the batteries need to be changed.

There are also rare cases when the batteries can become so old that they begin to leak acid into the thermostat, causing further issues.

The Thermostat has a Blown Fuse

Often, constant resetting or other issues can be pinned down to a blown fuse. When your thermostat blows a fuse, it will not function correctly, and many times it will reset to a specific temperature.

To check for a blown fuse, open up the thermostat and try and look for a clear small cylinder. While the location of the fuse will vary for each thermostat model and brand, it’s typically a colored fuse that will have a small filament inside of it.

If this filament has a crack, you will need to replace the fuse with a new one. You may be able to replace the fuse yourself in a matter of minutes. However, if you are not familiar with or have any background working with electrical components, it’s best to leave this task to an electrical professional. Note that this is a relatively small fix, so the job shouldn’t take long to perform.

The Thermostat has Wiring Issues

The wiring in an older thermostat can become loose and faulty, which can instigate issues with the unit itself. This problem may be difficult for you to diagnose unless it’s a wire that is visibly loose or damaged.

In some cases, the wires can simply go out and fail to provide continuity. If the latter is the case, you’ll need to contact an HVAC technician or electrician to have them replace the wiring or the thermostat if needed.

Why Does my Thermostat Keep Resetting Itself?

A thermostat set to 68 degrees for the kitchen area

If your thermostat keeps resetting itself, the chances are that it is either needs to be reprogrammed, has bad batteries, bad wiring, or a bad fuse. It’s best to troubleshoot all of these issues before reaching out to a technician, as it may save you time on repair costs.

How Do you Know a Thermostat is Bad?

Often a thermostat will display signs that it is due for a replacement. Here are the most common ones:

The HVAC System Keeps Powering On and Off

The main function of your thermostat is to communicate with its HVAC system. If the air conditioning keeps powering on and off, it’s likely that the problem is with the thermostat.

More often than not, it’ll be related to damaged or frayed wires or a bad battery. It’s best to have the thermostat inspected as soon as possible to prevent the issue from becoming worse. You can also perform your troubleshooting before reaching out to a technician.

Incorrect Temperature Readings

A thermostat showing faulty readings is a clear sign that it is going bad. If your thermostat begins registering incorrect temperatures, try resetting the unit and changing the batteries. If neither of these methods works, you may need to reach out to a technician. The thermostat can have bad wiring, or you may need to replace it entirely.

It’s Constantly Changing Temperatures

A faulty thermostat will have a difficult time maintaining accurate temperature settings. It may continuously change without any warning or fail to reach the correct temperature after programming. You can try reprogramming the thermostat and doing a reset with the circuit breaker. If the problem continues, it’s best to call a technician.

The HVAC System Keeps Short Cycling

A short cycling thermostat is typically faulty or old. Recycling refers to when the HVAC system repeatedly shuts on and off earlier than it’s supposed to.

For example, if your thermostat repeatedly shuts off after operating for 5 minutes and then turns back on 2 minutes later, it may have been short cycling issue. Short cycling can also be caused by bad wiring, but it’s typically caused by a thermostat that has simply run its course.

Why Does my Thermostat Keep Dropping Temperature?

A thermostat set to 68 degrees in the living room area

If your thermostat is having trouble keeping the correct temperature, it may need recalibration. The issue could also be that the thermostat is set to a pre-programmed temperature that you’ll need to readjust. Take a look at your instruction manual to determine how to recalibrate the thermostat.

Lastly, the thermostat can also be broken or old and due for a replacement. If your thermostat is over ten years old and suddenly starts to display signs that it’s faulty, you may want to have it inspected by an HVAC technician.

Common signs include dropping temperatures, turning on and off, and short cycling.

The Outdoor Unit is Frozen

During extremely cold temperatures coming into the thermostat may drop below its setting due to a frozen outdoor unit. If the evaporator coils in the outdoor unit are blocked by ice, the unit will not be able to transfer heat using the refrigerant inside of them. As a result, the thermostat will not be able to raise and maintain the temperature of the home. You’ll need to clear the coils to fix this issue.

An Incorrectly-sized Furnace

Sometimes a furnace will drop below its set temperature due to the furnace being the wrong size. An inappropriately sized furnace can cause serious issues inside a home.

For example, if the furnace is too small, it will lack the power to sufficiently heat the home, causing the thermostat to fail to reach the desired temperature. Conversely, a furnace that is too large may warm the air too quickly, causing it to overheat faster than the thermostat anticipates.

How Do I Reset the Thermostat on my AC?

You can perform a reset on your thermostat in one of two ways. You can press the reset button on the thermostat itself, granted the thermostat has a reset button. Or, you can perform a manual reset using the circuit breaker box. To do this, locate your circuit breaker and a d control for your HVAC system. Make sure the HVAC system is off first.

Next, find the control label for the HVAC system and flip the circuit breaker to the off position. Then wait 30 to 40 seconds and slip it back to the on position. Then turn the HVAC system back on.

When Should I Reset my Thermostat?

You should set your thermostat if you have a power failure in your home or if you are looking to troubleshoot an HVAC system issue. You may also need to reprogram the unit if it has been pre-programmed previously.

How Much Does a Thermostat Cost to Replace?

The cost of a thermostatic self will vary by brand and model, though it can range anywhere from $20 to over $200. The cost to have a contractor replacement for you will typically range anywhere from $50 to $150 and more.

Wrapping Things Up

We hope that this post has helped illustrate the most common reasons why a thermostat will keep resetting to 85°. Remember, It’s always best to troubleshoot the thermostat as best as possible on your own before reaching out to the pros.

Before you go, be sure to check out some of our other posts:

Do Central Air Conditioners Bring In Outside Air?

How Long Does A Central Air Conditioner Last In Florida?

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