The high pressure switch protects the A/C system. The high pressure switch is a dual function four wire switch. The high pressure switch turns OFF the A/C compressor and engages the condenser fan motor when line pressure exceeds 2965 kPa (430 psi).

For the condenser fan relay to close its internal contacts to supply the condenser fan motor with battery positive voltage, the A/C high pressure switch must be closed before it can provide a ground path for the relay coil.

The following conditions must be met in order for the condenser fan to activate:

Schematic Reference

HVAC Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Electrical Information Reference

Scan Tool Reference

Control Module References for scan tool information

1. Ignition OFF, disconnect the CONDENSER FAN relay.
2. Ignition ON, A/C request switch ON, verify that a test lamp does not illuminate between the relay controlled output circuit terminal and ground.

⇒	If the test lamp illuminates, test the relay controlled output circuit for a short to voltage.

3. Verify that a test lamp illuminates between the relay coil ignition circuit terminal and ground.

⇒	If the test lamp does not illuminate, test the relay coil ignition circuit for a short to ground or an open/high resistance. If the signal circuit tests normal, refer to Blower Motor Malfunction.

4. Verify that a test lamp illuminates between the relay switch B+ circuit terminal and ground.

⇒	If the test lamp does not illuminate, test the relay switch B+ circuit for a short to ground or an open/high resistance.

5. Ignition OFF, disconnect the harness connector at the condenser fan motor.
6. Test for less than 1.0 ohm between the ground circuit terminal 5 and ground.

⇒	If greater than the specified range, test the ground circuit for an open/high resistance.

7. Connect the harness connector at the condenser fan motor.
8. Ignition ON, connect a 20A fused jumper wire between the relay switch B+ circuit terminal and the relay controlled output circuit terminal. Verify the condenser fan motor is activated.

⇒	If the condenser fan motor does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, replace the condenser fan motor.

9. Ignition OFF, connect the CONDENSER FAN relay and disconnect the A/C high pressure switch.
10. Ignition ON, test for ignition voltage between the control circuit terminal 2 and ground.

⇒	If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, test or replace the CONDENSER FAN relay.

11. Ignition OFF, connect the A/C high pressure switch. Disconnect the harness connector X2 at the HVAC control assembly.
12. Ignition ON, test for ignition voltage between the control circuit terminal 3 and ground.

⇒	If the test lamp does not illuminate, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the A/C high pressure switch.

13. If all circuits test normal, replace the HVAC control assembly.

Relay Test

1. Ignition OFF, disconnect the CONDENSER FAN relay.
2. Test for 60-180 ohms between terminals 85 and 86.

⇒	If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If not the specified value, replace the relay.

4. Install a 30-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2 ohms between terminals 30 and 87.

⇒	If greater than the specified range, replace the relay.

Condenser Fan Motor

1. Ignition OFF, disconnect the harness connector at the condenser fan motor.
2. Install a 20-amp fused jumper wire between the relay controlled output circuit terminal 6 and 12 volts. Install a jumper wire between the ground circuit terminal 5 and ground. Verify the condenser fan activates.

⇒	If the condenser fan does not activate, replace the condenser fan motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.