Car ac pressure switch

How to detect malfunction of the refrigerant pressure sensor

In most cases, detecting a malfunction of the refrigerant pressure sensor requires computer diagnostics at a service station. Special equipment is connected to the vehicle which measures pressure of the refrigerant and oil content in it. If their levels are normal, diagnostics of the component is performed. Malfunction of the sensor-converter is determined using an oscilloscope. Failure of the conventional analog sensor is detected with an ohmmeter, but, for this purpose, the current pressure level in the air conditioner should be known. Low-pressure sensor passes the signal at 1.2–1.4 atmospheres and above, high-pressure sensor - at 20 atmospheres and below.

You may notice that the refrigerant pressure sensor needs diagnostics by the following symptoms:

• malfunctions of the compressor;
• compressor switches on without refrigerant;
• incorrect operation of the fan;
• corresponding signal of the indicator on the instrument panel, or an error message on the onboard computer;
• refrigerant leakage;
• air conditioner spontaneously switches off.

The reasons of refrigerant pressure sensor malfunction

A common malfunction of the refrigerant pressure sensor is a worn sealing ring. Over time, the rubber it is made of loses its elasticity, therefore refrigerant starts leaking from the joint. To avoid premature wear, it is recommended to buy only high-quality components, and to fill the system only with the refrigerant that is recommended by the vehicle manufacturer.

Component failure may be caused by fouling. The products of wear of compressor elements and other components of the air conditioning system are accumulated, and not only reduce sensor sensitivity, but also accelerate destruction of the sensor body. Therefore, refrigerant and filters should be replaced in due time, and the oil level in the compressor should be monitored.

Due to the loss of tightness of the sensor body, moisture and dirt get inside the component, which results in terminals oxidation, jamming of the moving parts, and increased risk of short circuit. Also, wires and connectors often fail due to mechanical damage.

Replacement of the refrigerant pressure sensor

The component is not repairable. A faulty component is to be replaced. Installing a new sensor can be done by yourself. However, on many cars you will have to drain the refrigerant, and then to fill the air conditioning system with the new one, so it is better to seek help from professionals.

If the threaded fitting into which the sensor is installed is equipped with a special nipple to prevent refrigerant leakage, you can replace the component yourself. To do this, follow the following instructions:

1. Put the vehicle on an inspection pit or a car ramp.
2. Stop the engine.
3. Open access to the component's location. To learn more about doing it, see the technical documentation for the vehicle.
4. Quickly, trying to avoid refrigerant leaks, remove the faulty component.
5. Install a new one; do not forget to lubricate the o-ring with compressor oil.