How do I check the air conditioner pressure sensor myself

How do I check the air conditioner pressure sensor myself?

Pressure sensors are indispensable assistants responsible for the proper operation of the entire air conditioner installed in the car. If the air conditioner in your car is unstable or refuses to turn on at all, it is likely that it is the sensors. In this article, we will tell you in detail how to check the pressure sensors of air conditioners yourself and what nuances you need to take into account.

Comprehensive verification


The first thing you need to check is the pressure. Thanks to this parameter, you can find out, how much refrigerant is in the system. If you have a pressure gauge, use it. Connect the device to the line responsible for low pressure. The minimum number that the pressure gauge should give out is 1.2 Atm. At this value, the air conditioner will start, but it will work poorly. However, start from this figure, because at home it is the only correct option.

pressure sensor check

Power supply

Find the electrical diagram of the air conditioning system of your car model to understand, what type of sensor is installed in the car. Only then will you be able to check the power and voltage.

If you have a two-pin sensor, then its electrical connector on one wire will be a plus, and on the other a minus. Knowing these features, you can check the availability of power using a multimeter, after switching it to the DC measurement mode. On four -pin sensors, two wires will be positive, and the rest will be negative.

All pressure sensors, regardless of their type, can be powered from five or twelve volts. If the sensors are not powered during the test, then the problem may be in the relay, fuse, control unit or in a banal wire break.


Using the same multimeter, you can check the voltage in the two-pin sensor. Put the connector on the sensor. If the pressure is all right, then you will see the minimum resistance between the sensor pins. When checking the four contact sensors, the logic is the same. The only important nuance that you need to know in advance is at what value of the refrigerant pressure the contacts open and close.

voltage check кондиционера

If you have a three-pin sensor, you can also check it with a multimeter. First, switch the device to the DC measurement mode. If the pressure is there, but there is no voltage, then the sensor needs to be replaced, it is faulty.

All of these recommendations apply to low-pressure sensors. To check the high- pressure sensor, you will need an oscilloscope. We recommend that you entrust this work to professional professionals specialists.

Please note

Many modern cars have technological air conditioning systems, which are equipped with a self-diagnosis function from the factory. Such a system can track the signal level, so that you can detect a breakdown in time.

To perform such a diagnosis, you need to purchase special equipment that is connected to the OBD-II connector. If you are lucky enough to have one for your own personal needs,

try to find faults in this way. If you notice in the diagnostic system that the electrical circuit is faulty, which means that the sensor has failed, or its wire has broken.


Now you know how to check the air conditioner sensors with your own hands. To perform a full diagnosis, you will have to go to the car service. But if this is not possible, you can try to perform the first check yourself. So you can determine whether the sensors are the cause of the air conditioner failure. Good luck!

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