How To Easily Test A Car A/C Pressure Sensor


A/C pressure sensors switch off a vehicle’s A/C system when refrigerant pressure falls below a certain threshold. In addition to warning the user about insufficient refrigerant, this also stops the compressor from working with inadequate lubricant. If the AC pressure switch is tripped, the compressor may freeze due to a lack of lubrication, necessitating expert servicing. If you believe that your car’s A/C pressure sensor is defective but are unsure how to determine it, read on to learn how to test a car’s A/C pressure sensor.

Signs of a Bad A/C Pressure Sensor

If you believe that your car has a faulty A/C pressure sensor, keep an eye out for the following signs:

  • Poor A/C functionality
  • The A/C system doesn’t produce enough chilled air
  • Strange noises from the A/C unit

How to Check a Car A/C Pressure Sensor?

Here’s a quick guide to testing your vehicle’s air conditioning pressure sensor:

What You’ll Need

  • The OBD II Scanner

Step 1

Switch on your vehicle’s A/C while the engine is running. Then keep the car’s doors open to prevent the A/C unit from turning off. If the A/C shuts off and on suddenly, the pressure sensor may not be functioning properly.

Step 2

While the A/C is still on, pop the hood. Find the evaporator, which is a grille or block-type component linked to the compressor through tubes and hoses and includes a pulley and belt system. Feel for the two tubes that connect the evaporator to the firewall. If the tubes are warm, there is no refrigerant flowing through them, indicating that the refrigerant level is too low or the pressure sensor is malfunctioning.

Step 3

Coupling the low-pressure fitting with a low-pressure pressure gauge from a refrigerant recharge kit will allow you to measure the pressure in the A/C system. It can be easily identified by a capital “L” label and is situated between the compressor and the accumulator. Low pressure should register at least 56 psi (pounds per square inch) on an 80-degree day. If the pressure is at a sufficient level, your pressure sensor may be malfunctioning.

Step 4

Find your vehicle’s OBD II port, which is normally a few feet from the steering column. While some versions of vehicles include an OBD II port on the rear of the center console, others have it below and to the left of the steering wheel.

Step 5

Connect the OBD II scanner to the terminal and switch the vehicle’s ignition to the accessories mode. Sensor codes that appear on the OBD II scanner can be read immediately from the scanner or looked up on a website like Autozone or OBD II Code. If the air conditioner pressure sensor fails, the OBD II code will notify you via the scanner.

Step 6

Remove the A/C pressure sensor and examine the wire connection running to the sensor from your automobile’s electrical wiring. Switch the ignition key to the accessories position while placing the multimeter’s probes on the electrical connection’s harness end. If the sensor’s wiring is right, the multimeter should show a reading from 4.0 to 5.0 volts.

If you need help sourcing automotive parts, contact us today!