Car Temperature Gauge Goes Up And Down

The gauge showing your car’s temperature might be the most important in the vehicle. This gauge helps to prevent engine damage and warns you when it is overheating. You can pull your car over to let the engine cool off if the temperature goes up. What do you do if the temperature of your car goes up or down?

Temperature gauges can be affected by a poor thermostat or lack of coolant. It’s also possible that there is air in the cooling system. Alternately, it might be due to a deficient coolant temp sensor.

We will be discussing the issues that can lead to problems with temperature gauges in this guide. This guide will show you how to correct the problem as well as discuss the importance and benefits of diagnostics. 

What is the purpose of the car temperature gauge?

The engine temperature can be viewed by the car temperature gauge. It’s normally located on the dashboard, near the speedometer. It’s designed to measure the coolant temperature, helping you see how hot or cold the motor is at any given time. 

Coolant is circulated throughout the system by the water pump. It heats up when it's in an engine. Then, it’s cooled down when it gets to the radiator. To maintain the right temperature, the thermostat must stop or start the flow of coolant. There’s also a coolant temperature sensor found near the thermostat that sends the signal needed to create the gauge reading.

To determine whether the needle is in a good position, you must first know the engine's normal operating temperature. The gauge will be at the bottom when the engine is cool. The reading for most cars is at 122 degrees Fahrenheit. 

The engine heats up once you start driving. The engine heats up and the heat transfers to the coolant. This regulates the temperature. It will display between 180 to 220 degrees Fahrenheit once the engine is warm and it is operating normally. 

The coolant should stay at these temperatures until the engine is turned off. This is when the coolant ceases to flow and the temperature begins to drop. 

The Car Temperature Gauge Changes Between Up and Down

1. Bad Thermostat

To regulate coolant temperature, the thermostat is installed. It can fail and cause the temperature gauge to fluctuate. If it starts to fail, the gauge will not respond in this manner.

When the thermostat is stuck closed, the coolant isn’t able to flow, so the engine won’t get cooled off. The motor heats up because of this. 

Engine temperatures will drop to below the normal range if you leave your thermostat open. It is possible that you will have difficulty heating the HVAC system. 

RELATED: 5 Signs that a Car Thermostat is Not Working

2. Low Coolant

Too much water can cause the temperature gauge to behave oddly. While some people mix water with the coolant, it’s important that too much doesn’t get into the system.

Temperatures will rise if there isn't enough coolant. Because water can’t adequately carry the heat away from the engine as coolant does, you could see unusual fluctuations in the temperature. 

If the engine starts to overheat, it’s best to replace the coolant. Follow the recommended mixture of antifreeze and water based on your car’s service requirements. 

Related: How low is the engine coolant level? (Causes & Consequences)

3. Air in Cooling System

Air could cause temperature drops in your system. A defective or broken head gasket can allow air to enter the system. You can also let air infiltrate the cooling system by leaking in the radiator hose, or doing improper coolant flush procedures.

If the coolant gets trapped in the air pocket, it can cause the engine to heat up. The engine can be re-started once it is moving. 

4. Defective Temperature Gauge

It’s always possible that the temperature gauge itself is to blame. The instrument cluster isn’t the first thing to look at, but it always is a possibility if you can’t find anything else that’s wrong. 

You will often see problems with other gauges when your instrument cluster has issues. Take a look at the other gauges to see if there’s an electrical fault.

RELATED: Temperature Gauge Stays On Cold? (Causes & How to Fix It)

5. Faulty Temperature Sensor

It’s more likely that the faulty readings are coming from a malfunctioning coolant temperature sensor (CTS). It is located in the engine, and can get contaminated. 

The wrong signal could be sent if the sensor is damaged or corroded. If the sensor is not working properly, it can cause irregular readings.  

6. Bad Computer Module

A bad module in the computer could cause your temperature gauge to behave erratically. It is necessary to relay data from other vehicles and engines.

It’s the module’s job to relay data that moves the temperature gauge. You may notice strange problems if your module goes bad. This part controls many other systems.

How to fix fluctuating temperature gauge

1. Thermostat should be replaced

You will pay $125 to $300 on average to get your thermostat changed. However, it’s not a difficult job to do yourself.

Find the thermostat first. The thermostat is likely located at the junction of the engine's top radiator hose and the bottom radiator hose. Take off the clamp, and place the coolant into a bucket. 

Take out the thermostat, and replace it with a replacement gasket. Install the thermostat again, and then fill it with coolant. 

2. Filter Cooling System

On average, a professional coolant flush costs between $65-$150. You can also do this job at home. 

Fill the radiator with water. The vehicle should run for at least ten minutes. Then turn off the engine. Make sure to mix the appropriate amount of coolant in your system.

3. Bleed Cooling System

If you feel that air is getting stuck, it's possible to bleed your cooling system. You can remove the radiator cap. Fill it with as much coolant as you want. Turn the heat up to high and the fan on low. 

Keep topping up the coolant until the levels fall. To circulate coolant, loosen the bleed valves. Keep doing this until your temperature does not fluctuate. 

RELATED : How to Bleed Cars Cooling System (In 9 Simple Steps).

4. Change the temperature gauge sensor or gauge

Replacement of the temperature sensor cost should range from $200 to $450. You could need to change the coolant temperature sensor on the top or side of the engine, plus there’s a chance that the gauges themselves are to blame.

Before you replace parts, make sure to do proper diagnosis. Don't waste your money by doing unnecessary repairs. 

5. Replace the Computer Module

The most expensive option of all repair options. The average cost of a new Engine Controller Module is between $300-$1,500, including labor and parts.

A good code scanner should reveal if there’s an issue with the Engine Control Module. As the central hub fails, you may notice additional unusual symptoms.