Compressor Control (A/C Relay Signal) Inspection

A/C Compressor Control (A/C Relay Signal) Inspection

^ If the magnetic clutch, and A/C compressor idle-up do not operate, the failure is in the A/C amplifier, PCM, or related wiring harness.

B+: Battery positive voltage:

Step 1
1. Start the engine and press the AUTO switch on.
2. Press the defrost switch on and set the fan switch at manual 1st speed. Verify that the engine speed increases.
3. If the idle-up control operates, go to Step 2.
4. If the idle-up control does not operate, go to Step 9.


Step 2

1. Check the following fuses.







2. If a fuse is burnt, replace it after checking and repairing the wiring harness as necessary.
3. If the fuses are OK, go to Step 3.


Step 3
1. Remove the A/C relay.
2. Turn the ignition switch to ON and press the AUTO switch on.








3. Measure the voltage at terminal wires (R) and (R/W) of the A/C relay connector in the relay box.


Step 4
1. Remove the A/C relay.








2. Connect battery positive voltage to the terminal A and ground the terminal B of the A/C relay.
3. Check for continuity between terminals C and D of the A/C relay.


Step 5





1. Connect a jumper wire between terminal wire L/W and a ground.
2. Turn the ignition switch to ON, and press the AUTO switch on.
3. If the A/C compressor operates, repair the wiring harness and/or check the PCM.
4. If the A/C compressor does not operate, go to Step 6.


Step 6
1. Turn the ignition switch to ON, and press the AUTO switch on.
2. Set the temperature at 18°C {65°F}.








3. Measure the voltage at terminal wire (LG) of the magnetic clutch connector.


Step 7
1. Disconnect the refrigerant pressure switch connector.





2. Connect a jumper wire between terminals of the connector as shown.
3. Turn the ignition switch to ON and press the AUTO switch on.
4. Set the temperature at 18°C {65°F}.
5. If the A/C compressor operates, measure the refrigerant pressure.
If the pressure is normal, replace the refrigerant pressure switch.
6. If the A/C compressor does not operate, go to Step 8.


Step 8
1. Disconnect the refrigerant pressure switch connector.
2. Turn the ignition switch to ON.








3. Measure the voltage at terminal wire (G/W) of the connector.


Step 9
1. Disconnect the refrigerant pressure switch connector.
2. Turn the ignition switch to ON, and press the AUTO switch on.
3. Set the temperature at 18°C {65°F}.








4. Measure the voltage at terminal wire (G/W) of the connector.


Step 10
1. Turn the ignition switch to ON, and press the AUTO switch on.
2. Set the temperature at 18°C {65°F}.








3. Measure the voltage at terminal wire (B/O) of the A/C amplifier connector.