Why Car Temperature Gauge Goes Up and Down

In this article, we are going to answer the question, why car temperature gauge goes up and down.

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A car’s temperature gauge is one of the most important gauges in your vehicle. It tells you when your car overheats. So that you can stop and let it cool before it becomes a major issue. However, if the gauge goes up and down randomly, then there may be an underlying problem that needs to be addressed.

What causes Car Temperature Gauge to go up and down?

Just like driving with a bad speed sensor. A faulty car temperature gauge is a safety risk for any driver.

There are a couple of things that can cause your temperature gauge to go up and down. The main problem lies withing your car’s cooling system. It could be faulty wiring or the fact that the temperature gauge; or the thermostat itself is worn out or needs to be replaced. It could also be a bad coolant temperature sensor (CTS). You need to narrow down the possible causes and find the culprit and fix it.

1. A malfunctioning thermostat

A car’s thermostat controls the temperature of the coolant within the engine, so if it malfunctions, then you may end up with an inconsistent display on your thermometer. When you have a faulty thermostat valve, you will most likely see that your gauge temperature jumps around erratically when there is no reason for it to do so.

This type of issue will not make your vehicle overheat, and you can usually drive around this problem for some time before you need to take it in to be repaired. If the thermostat goes out all at once, then there is a chance that more serious issues with your engine are taking place.

To fix this issue, you’ll need to have your thermostat replaced. Here’s a video on how to replace a thermostat in ’05-’11 Honda Civic.

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2. A damaged water pump

If your temp gauge is always going up and down no matter what, you’re probably not facing a thermostat problem. You may have a faulty water pump or bad radiator cap instead. 

A faulty water pump can make your car overheat consistently, while the other two issues could mean it’s under-cooling for some reason. Again, this means that someone should look at your vehicle to see why it’s doing this.

There are two sensors you can look at: one for the cooling system, and another for engine overheating. If either of them is giving faulty readings then they should be replaced as soon as possible.

The other main cause is a faulty ignition switch, which controls how much power your gauges receive. Have someone check this out too if you’re still not getting anywhere with checking the sensors manually.

3. Low water in the cooling system

Another cause of a temperature gauge that goes up and down at random is water in the cooling system. If your engine doesn’t have enough coolant flowing through it, then the temperature will increase to unsafe levels and your car will overheat quickly. Engine coolant is one of the most important fluids that you need to ensure that is at optimum level.

Coolant is used to help release heat from the engine so that the radiator can pump it out into the air outside safely. When there isn’t enough coolant, or if it gets lost somewhere in the system, this causes overheating.

The warning signs are usually that your temp gauge will go up when you start driving but will then come back down after a few minutes of normal operation. As long as you don’t drive too hard for too long then all should be well.

On the other hand, if your engine is consistently overheating then you should look to replace the coolant right away. This will ensure that your radiator and cooling system work at full efficiency again. Be sure to check the level too – it’s not just about replacing one part.

4. Air trapped in the cooling system

Take the car out for a drive, let it sit in traffic for half an hour or so, then check on the temperature gauge. If the gauge has gone down then you have air trapped somewhere along with your cooling system. Find out where and fix it as soon as possible.

Internal corrosion in the radiator or engine parts. This damage is tougher to find because internal parts aren’t always visible. But look at them closely anyway if nothing else will show signs of being worn down. The only way to repair this is to replace those parts altogether.

If you can’t figure out exactly which part is causing your temperature gauge to go up and down, just get someone to take a look at your vehicle. Tell them that you want a full inspection so they can check out all of the components. It’s better to spend a few bucks now than hundreds of later.

5. A partially plugged-up radiator

Another cause of temperature gauge problems is a partially blocked radiator. This prevents the engine from getting all of the coolants it needs. If you let this go on long enough then it can cause serious damage to your engine and its other parts.

When checking for a partial blockage, make sure that you don’t have any crumpled or damaged hoses in the cooling system. Cracks in these tubes are bad enough without additional dirt clogging them up further.

Also, look out for small leaves or tree debris; if they get caught anywhere near the cooling fan then they will affect how much air gets through. If a hose isn’t entirely blocked but has been damaged by exposed metalwork, this can be fixed quite easily with some tape.

Just wrap a few layers of duct tape around the hose until it is again covered by plastic, and your engine will be able to run at normal efficiency.

6. A bad temperature gauge

Another possible cause of temperature gauge problems is a bad temperature gauge itself. This may be an obvious one, but it is worth checking if you aren’t sure what else could be wrong.

A corroded or damaged sensor can also mess up your gauges, so always check this too. Also, check your connections just to make sure that everything isn’t loose and flapping about in the breeze; this would allow your engine to get overheated quickly because of all the extra friction.

If it turns out that your temperature gauge is working perfectly fine then countless other things could still cause problems. This is why we recommend getting someone qualified to look at your vehicle; only they will be able to identify the source of your temperature gauge issues properly.

7. Defective computer module

If you have a hotter engine and the temperature gauge is not going up or down, the computer module could be defective on your car. 

A computer module is responsible for communicating information between the engine and other computer modules in your car. This will be needed to drive the temperature gauge on your dashboard. 

If you are having this problem, do not ignore it as it could lead to serious damage that would cost you a lot more in repairs than a new computer module

To diagnose your problem you can use a certified scanner. A technician will hook your car up to the computer and it will scan through all of your systems to determine if there is any trouble with your computer module. 

If the scan comes back that nothing is wrong, then chances are that one of the other components may be bad or affecting how everything else works together.

If this turns out to be true, then there’s not much you can do about this beyond taking your car to someone who knows what they are doing. The real question now is whether anyone close by has the knowledge required to fix such a complicated machine.


The temperature gauge in your car goes up and down depending on the outside temperature. This is normal, but if it’s not going back to a normal range then you might have an issue with your radiator or cooling system. 

If this is the case, don’t ignore it! The quicker you get repairs done before more damage happens, the less expensive it will be for you. We hope this article helped answer some of your questions about what could cause that pesky temp gauge to go haywire and how to fix things when they do go wrong.

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