Coolant temperature gauge not working or at a low level

There are situations in which the drivers can see that the car’s coolant/antifreeze temperature gauge they own remains at a low level or does not work at all.

If you face such a problem you should know that the cooling agent works every time at a constant temperature when the engine is hot. The role of this coolant is to help the engine run as efficiently as possible.

It is known, however, that over time certain components of the car wear out, so is the temperature gauge of the coolant may fail over time, so in the next lines of this article we will discuss this aspect, and you will be able to find out which are the reasons why this gauge remains low and you can find out if you go through the article with us until the end, and how to solve this problem.

The role of the cooling temp gauge

reasons why coolant temp is at a low level

It is very important that, first of all, you know the role of this gauge, because finding out what its role is and how it works will be much easier for you.

Therefore, devices that measure temperature differ from one car model to another. If you own an old car, you will usually find a coolant temperature sensor that comes with two wires that go directly into the cluster.

This is possible because old cars do not have a motor control unit like new cars do, the control unit that uses the temperature of the cooling agent as information.

As for modern cars, they are provided with the engine control unit (ECU), and this requires the temperature of the coolant as information to calculate the required fuel at all different temperatures.

It is very important to understand that the wire from the temperature sensor of the cooling agent may first of all pass to the control unit of the engine, and then the information will be directed to the cluster.

Depending on the make and model of the car there are different configurations, and Asian cars such as Nissan, for example, use two coolant temperature sensors, one for instant gauge and one for the control unit.

In several cases, four-wire temperature sensors can be found, which have the role of transmitting information directly to the control unit of the engine, but also the instrument cluster.

Well, we’ve already talked about this aspect a lot, so we’ll see below why the engine temperature gauge remains at a low level.

Some reasons are common, others are less common, so we will see in the following lines.

1. Bad coolant temperature sensor

The most common problem when the car has a faulty engine temperature reading is due to the coolant temperature sensor, which is faulty and sends erroneous information to the cluster instrument.

2. Faulty cluster

Another possible problem is that the car has a faulty temperature gauge. Even so, several temperature sensors are part of the instrument cluster of modern cars, and in certain situations, the temperature gauge can be replaced or any problems found can be repaired.

There are also situations in which it is necessary to replace the group of instruments, and for this problem, it would be advisable to deal with the specialists so that everything is done by the book.

3. Broken cables to sensor or gauge

As I said before with a few lines in this article, the wires either go from the sensor to the cluster or to the motor control unit, which is why you have to check if there are any broken cables between these components.

The simplest is to use a multimeter from all wires. To use such an extremely important tool you do not have to be mechanic, but you still need to know a little about the car and have knowledge about electronics.

Otherwise, it would be advisable to take the car to an authorized workshop or a mechanic to handle the problem.

4. Bad thermostat

The role of the thermostat is to restrict the cooling liquid to flow through the radiator. Under the conditions in which the thermostat is locked open, the chances are very high that the temperature will not reach an optimum value.

Under these conditions, the temperature will increase slightly from the minimum if you drive the car more aggressively. If the temperature indicator rises slowly, then the chances of the thermostat having a problem are very high.

5. Corrosion between connectors

Another possible problem is the corrosion between the connectors. In this case, it is very important to clean and spray the electronic cleaning device in the sensor connector, but also the cluster connector and the motor control unit connector.

In the situation where there is corrosion in these places, there are very high chances of having a problem with the seals of the connectors. In this case, it may be necessary to check the connectors to repair as soon as possible, if necessary.

6. The presence of air in the cooling system

Another very important aspect is that the air, if it is found in the cooling system of the car, can cause the temperature measurement to remain cold if there are air bubbles in the sensor’s place.

In the conditions where there is, or you suspect that there would be air in the cooling system of the car it is very important to drain the cooling system.

7. A bad electronic control unit (ECU)

It may happen that over time and for different reasons, the control unit of the car may be damaged if the temperature information first reaches ECM, which then delivers the information to the cluster.

If necessary, perform an error code check, and to do this you need an OBD2 scanner, from the engine control unit, so you can see if it receives the temperature information.

If the temperature control unit is located in the engine control unit, but in the control group no, it is very important to check that these two components use the same sensor.

To do this, it is necessary to measure the temperature output from the engine control unit, and this should be done by a car electronics expert.

It is definitely not necessary to replace the engine control unit if it is not defective, especially since this component is very expensive and requires coding.


Therefore, the first thing to do if you see that the coolant’s temperature gauge is at a low level or it is not working is to check if this indicator is working properly. You can follow all the steps I listed in this article, so you do not have to go to a car workshop and spend money to pay the labor.

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