5 Signs Your Thermostat Is Broken (2024)

Your vehicle’s thermostat is a vital tool that is designed for measuring the temperature of the coolant in the engine. You can usually find the corresponding thermostat gauge, or dial, on the dashboard. This gauge tells you what the thermostat readings are and whether you may have an issue.

Specifically, the dial alerts you about the state of the coolant–whether it is too cool, normal, or if it is overheating. If the gauge shows a too low or high reading then you need to look into whether the thermostat is working properly, or if you have a corresponding issue in the engine. If you ignore a faulty thermostat it could cause further damage to the operation and functionality of your engine.

A high reading on the temperature gauge could mean any number of problems from a coolant leak, a water pump malfunction, or broken thermostat gauge. It could be displaying an inaccurate temperature. In this case, your car may not be overheating, but your temperature gauge won’t be able to warn you.

Thermostats can often go bad after about 10 years of use. If you have either bought an older vehicle or you have not checked yours in a long time, then you need to be able to recognize the signs that the thermostat may not be working. Here are five easily recognizable signs that will alert you that the thermostat needs fixing.

1. You Notice Erratic Temperature Changes

Your vehicle’s thermostat may also affect the temperature of the air coming from your air conditioning and heating systems. If you notice sudden and erratic temperature changes from cold to hot or hot to cold, then it could be a sign that your thermostat has stopped working correctly. Get your vehicle inspected if you notice these extreme temperature changes in your vehicle interior.

2. You Find Incorrect Readings on the Temperature Gauge

The temperature gauge will read cold until your vehicle has had time to warm up, after which, it should register the average temperature. If it continues to read too cold or registers too hot, then there is the chance that the temperature gauge should be replaced. If working correctly and your vehicle keeps overheating, then there may be an issue with the coolant or engine itself. If too cold, then the thermostat could be stuck open, causing overcooling. In this case, the thermostat may also need replacing.

3. Your Vehicle Makes Concerning Noises

It is never a good sign when your vehicle makes irregular sounds. If your thermostat is not working properly, you might hear rumbling sounds coming from the engine because the coolant in the radiator is boiling. It could sound like knocking, boiling, or gurgling. Any of these could point to a serious problem in your cooling system because your thermostat isn’t reading the coolant temperature correctly.

4. You Find Coolant Leaks

If the thermostat fails in its closed position, then this can cause the coolant to overflow and leak out of the thermostat container when the engine overheats. If you find coolant leakage, it could be a sign that the thermostat has broken and requires replacement. The easiest way to see whether your vehicle is leaking coolant is to check underneath the vehicle. If you find red-ish or green-ish appearing liquid staining the ground, you probably have a coolant leakage problem.
If you avoid getting this problem fixed, then you will begin to have a leaking problem with the coolant hoses, and this could continue to affect other related parts. If you find coolant leaks under your vehicle, then be sure to visit your local Salt Lake auto repair store.

5. You Notice Problems with the Heating System

If driving during the winter or in a cooler climate, your thermostat may get stuck in an open position which will affect the heating system. If stuck open, the thermostat will allow coolant to continue to flow into the engine, even when it doesn’t require more coolant. If this happens, and you turn the heater on simultaneously, then only cool air will come out of the vents, no matter how high you turn up the heat.
In cases where you don’t require hot air blowing out the vents, you can still check to see if the thermostat is stuck open. Look at the needle on the thermostat gauge and see whether it moves slowly before it stops before the normal point on the gauge. If this is the case, then crank up the heater to see if it blows hot or cold air. If it blows cold air, then most likely the thermostat is broken.

Because so many other engine parts rely on the thermostat’s functionality and readings, you should be sure to get the thermostat looked at or replaced if you think it might be faulty. Otherwise, your engine could suffer irreversible damage and other serious problems.

Contact your mechanic today at Burt Brothers to get the best Utah auto repair services and shop tires at any of our 14 locations from Park City to Sandy.

5 Signs Your Thermostat Is Broken (2024)

FAQs

5 Signs Your Thermostat Is Broken? ›

A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.

What are the symptoms of a broken thermostat? ›

A bad thermostat can be detected when your AC or furnace is not turning on, your HVAC systems are not turning off, the thermostat not responding, your HVAC system is short-cycling, the room temperature not matching the temperature displayed on the thermostat, and the programmed setting resetting themselves.

How do you know when your thermostat needs to be replaced? ›

If you make changes at the thermostat and get no response whatsoever from your furnace, air conditioner, or heat pump, it could mean the thermostat is bad. Thermostat doesn't respond to changed settings: When you make temperature settings at your thermostat, it should almost immediately respond to those changes.

What is a common problem with thermostat? ›

The Thermostat Is Dirty

Thermostats, like many other electrical appliances, will malfunction if they're allowed to get too dirty. Dirt, dust, and debris can pose problems for both electrical and mechanical components, causing your thermostat to fail. Turn off the power source and remove the thermostat's cover.

How does a car act when the thermostat is bad? ›

Overheating is the most common symptom of a failing thermostat. Due to corrosion or aging, your car's thermostat can get stuck in a closed position. If this happens, the thermostat will not let the coolant reach the radiator, and, as mentioned above, the engine will overheat, causing severe damage.

What causes a thermostat to fail? ›

Power problems are one of the most common causes of thermostat failure. Whether your thermostat is wired to the mains or runs on batteries, a lack of power will stop your thermostat from accepting commands and communicating with your HVAC system.

How common is it for a thermostat to go bad? ›

As with any system, eventually, your thermostat will become outdated. Modern home thermostats tend to have about a 10-year lifespan but are usually replaced sooner due to innovations in the market.

What happens when a thermostat fails? ›

A properly functioning thermostat regulates coolant flow to the heater core, allowing it to provide warm air to the cabin. Low Coolant Levels: A failing thermostat can cause coolant to get trapped in the engine, leading to low coolant levels in the radiator.

Can a bad thermostat cause house not to cool? ›

When your thermostat is working correctly, you can keep it as cool or warm as you need. A bad thermostat can cause your AC to not cool or heat the room to the desired temperature. Air conditioning concerns are more apparent: Your thermostat is one of the best indicators of your air conditioning system's health.

What is the lifespan of a thermostat? ›

As with all other systems, your thermostat will eventually become old and outdated. The lifespan of most home thermostats is 10 years. However, you may need to replace yours sooner as newer, more efficient thermostats enter the market.

Will a bad thermostat throw a code? ›

The exact location of the thermostat and issues related to a damaged thermostat may vary depending on your vehicle. For most vehicles, trouble code P0125 is related to this issue as well.

How do I know if my thermostat is stuck open or closed? ›

If you see the coolant flowing through the radiator, then the thermostat opened and is working properly. If not, then it is most likely stuck closed. If you can't tell if the coolant in the radiator is flowing, shine a flashlight inside so you can see it better.

What happens when thermostat goes out in house? ›

Any time your air conditioner or furnace doesn't deliver the desired temperature, it could mean your home has a broken thermostat. A broken thermostat is more than an annoyance – it could quickly cause your house to get uncomfortably hot or cold, and it often leads to substantial energy waste as well.

What happens if you drive with a broken thermostat? ›

The longer you drive with a faulty thermostat, the more you risk causing significant damage to your car. The engine might overheat, causing the head gasket to fail or even leading to a cracked engine block. Both repairs are time-consuming and can be quite expensive, easily running into thousands of dollars.

How to tell if thermostat housing is bad? ›

Recognizing Signs of a Bad Thermostat Housing
  1. Higher Temperature Reading: A faulty temperature housing might fail to open or close correctly due to electrical problems. ...
  2. Coolant Leakage: ...
  3. Fluctuating Temperature Readings: ...
  4. Engine Overheating: ...
  5. Improper Coolant Circulation: ...
  6. Coolant Hoses Staying Cold:
Aug 14, 2023

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