A/C Pressure Sensor

Description and Operation

Description

The A/C pressure transducer (APT) measures the high-side line pressure and converts it into a voltage value. Based on the converted voltage value, the engine ECU controls the cooling fan, operating it at high or low speed. The engine ECU stops compressor operation when the refrigerant line temperature becomes excessively high or low to optimize the air conditioning system.

Repair Procedures

Inspection

Before measuring the refrigerant line pressure, check that the refrigerant amount is charged according to the specified charge amount. (Refer to Heating, Ventilation, Air Conditioning - "Specifications")

1. 1
   Turn the ignition off.
2. 2
   Connect the refrigerant recovery/recycling/recharging machine. (Refer to Air Conditioning System - "Repair Procedures")
3. 3
   Turn the ignition on and turn on the air conditioner.
4. 4
   Calculate the reference voltage using the high-pressure value of the recovery/recycling/recharging machine and the formula below.

   Reference voltage (V) = 0.0088 x pressure (psi) + 0.37

5. 5
   Measure the sensor output voltage between terminals "1" and "2".

   

   Pin No.	Function
   1	Ground
   2	Voltage
   3	Power supply (+5V)

6. 6
   If the reference voltage and the sensor output voltage are close to each other, the A/C pressure sensor is normal.
7. 7
   If the output voltage is 0 V, or the reference voltage and the sensor output voltage are not close to each other, replace the A/C pressure transducer.

   Check whether the output voltage changes when the high-side refrigerant line pressure changes.

Replacement

1. 1
   Disconnect the negative (-) battery terminal.
2. 2
   Recover the refrigerant using a recovery/recharging station.
3. 3
   Disconnect the air conditioner pressure sensor connector (A).

   

4. 4
   Remove the A/C pressure sensor (A).

   Tightening torque: 10 – 12 N·m

   

5. 5
   Install in the reverse order of removal.

   When installing, replace it with a new O-ring (A).