Temperature Gauge Stays On Cold? What Causes It? How to Fix It!

Is your coolant temperature gauge not staying on the cold side, even though it is clearly warm in your car?

It is important to check the coolant temperature in your car. Overheating can lead to serious engine damage.

We will be discussing the coolant temp gauge in this article and how to deal with it if you have an issue.

Índice de Contenido
  1. Seven Reasons Your Car's Temperature Gauge Keeps On Cold
    1. 1. Faulty Engine Temperature Sensor
    2. 2. Broken Wirings
    3. 3. Cluster/Faulty Gauge
    4. 4. Connectors for plugs are corroded
    5. 5. Bad Thermostat
    6. 6. Air in the Cooling system
    7. 7. Broken Engine Control Unit
  2. Most Frequently Asked Questions
    1. What is the worst thing about having my car's temperature drop?
    2. What can you do to unstick a thermostat stuck?
    3. How can I tell if my thermostat is open or closed?
    4. What is the best way to reset my temperature gauge?

Seven Reasons Your Car's Temperature Gauge Keeps On Cold

The most common reason why your car’s temperature gauge stays on cold is a faulty coolant temperature sensor. Bad wiring between the sensor and the cluster can cause it. Sometimes, the problem can be caused by a stuck thermostat that causes the engine to not heat properly.

Let’s go a little bit more into detail about the different causes. Below is a list that explains why a temperature sensor stays cold.

1. Faulty Engine Temperature Sensor

Coolant Temp Sensors

We discussed that the main problem when a low engine temperature reading occurs is in the coolant temperature sensor, which sends the data to the cluster.

Some models of cars are equipped with two temperature sensors while others have only one. The models with one sensor usually both use the engine control unit’s temperature and the same sensor for the gauge.

Two coolant temperature sensors are required for your vehicle model. One is used by temperature gauge and the other is used to control the engine.

It is easy to test engine temperature sensors with a multimeter. However, you must find the correct values. Your repair manual will often have more details on testing them.

However, if you decide to replace one of them, you should make sure that you replace the sensor going to the temperature gauge – if you have two.

2. Broken Wirings

Broken Wirings

If you have two temperature sensors on your car and one separate for the gauge, you need to check the sensor’s wires to the gauge or ohm measure the sensor from the cluster connector.

There could be one sensor that is working for them both, but it's possible there are problems with their wires. You should check for broken wires.

The best way to find broken wiring is to measure the resistance with a multimeter from all the wires’ directions. This requires some knowledge about electronic cars, so you might need to have your mechanic look at it. 

This information can be found in the repair manual. You can check the wiring diagram on your car to verify that you have measured correctly.

3. Cluster/Faulty Gauge

Instrument Cluster

A faulty temperature gauge is the next issue. Most temperature gauges can be integrated into the instrument cluster of modern cars. You can sometimes replace the temperature gauge, or fix any defective solderings that you discover.

You might need to replace an instrument cluster in other clusters. If your skills are not up to par, you can leave your instrument cluster with an expert who will repair it.

Although a faulty cluster may not be a common issue, they can often prove to be very costly and require coding. Before replacing the cluster, it's a good idea to look at the rest of the system.

If you are familiar with the subject, an Ohm tester can be used to test the temperature of your cluster using a gauge.

4. Connectors for plugs are corroded

Coolant Temperature Sensor Location

A faulty temperature gauge can also cause corrosion in connectors. Clean and spray electronic cleaner in the connector at the sensor, the engine control unit connector and the cluster’s connector.

If corrosion appears, there might be a problem with the connectors’ sealings, and you may have to take a look at these to make a permanent repair or replace them to avoid future problems.

5. Bad Thermostat

Thermostat Housing

The thermostat stops coolant flowing through radiators. This can cause the radiator to heat up too fast.

If you drive fast enough, your temperature will sometimes rise a little beyond the minimum mark. The thermostat might be faulty if your temperature is rising slowly. 

You can read more about thermostats here: Faulty Thermostat Symptoms & Causes

6. Air in the Cooling system

Bleeding Coolant System

The temperature gauge can become colder if the coolant is too hot. You can usually see this with the fluctuating coolant temp gauge.

You must bleed the coolant system if you suspect there is air. This guide will help you learn all about coolant bleeding.

7. Broken Engine Control Unit

Engine Control Unit

If your vehicle has one temperature sensor and two pins, this applies only.

Your engine control module could have a problem in rare instances. If temperature information is not received before the ECM, the ECM sends it to the cluster.

To determine if your engine control unit is receiving temperature information, check the OBD2 scanner on the engine control units to confirm that this code has been checked. 

You must ensure that the two sensors are working together if you find temperature readings at the engine control unit and not the cluster. You will need to test the temperature output of the engine control device if this happens. It is best to have a professional car electronics technician do it. 

You do not want to replace the engine control unit if there’s no problem with it because they’re often costly and require coding.

Most Frequently Asked Questions

What is the worst thing about having my car's temperature drop?

Yes, if your thermostat is stuck open and the engine never gets up to operating temperature, it’s bad for the engine and fuel consumption in the long run. It will be more efficient and wear-less for the engine parts if it is at operating temperature.

What can you do to unstick a thermostat stuck?

It is possible to remove a stuck thermostat manually. But if your thermostat is stuck, you’ll most likely want to replace it, or you could end up in the same situation in the near future, and they are quite inexpensive.

How can I tell if my thermostat is open or closed?

Checking the outlet radiator line can help you determine if your thermostat has become stuck. While the engine heats up, coolant should not circulate through the hose. It should be kept cold until it reaches its operating temperature. It is likely to be stuck open if it is at the same temperature during heating.

What is the best way to reset my temperature gauge?

Most car models have no means to reset the temperature gauge. If you have a rare car model where it’s possible you need to check a repair manual for your particular car model.

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