For 1990-2009 cars

Table 1: | Compressor Control Module Voltage Table

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the HVAC System Check performed? | -- | Go to Step 2 | Go to HVAC System Check
2 |

1. Turn the ignition switch to the ON position.
2. Backprobe A/C the compressor clutch connector with a test lamp from the connector cavity to chassis ground.

Does the test lamp light?

--

Go to Step 40

Go to Step 3

3 | Backprobe the A/C compressor clutch relay connector with a test lamp from cavity 4 to chassis ground. Does the test lamp light? | -- | Go to Step 4 | Go to Step 5
4 | Repair the open in the BLK/WHT wire between the A/C compressor clutch relay and the A/C compressor clutch. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
5 | Backprobe the A/C compressor clutch relay connector with a test lamp from cavity 2 to chassis ground. Does the test lamp light? | -- | Go to Step 7 | Go to Step 6
6 | Repair the open in the RED wire between the A/C compressor clutch relay and fuse block 1. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
7 | Backprobe the refrigerant pressure switch connector with a test lamp from cavity 1 and chassis ground. Does the test lamp light? | -- | Go to Step 9 | Go to Step 8
8 | Repair the open in the LT GRN wire between the refrigerant pressure switch and fuse block 2. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
9 | Backprobe the refrigerant pressure switch connector with a test lamp from cavity 2 to chassis ground. Does the test lamp light? | -- | Go to Step 11 | Go to Step 10
10 | Replace the refrigerant pressure switch. Refer to Pressure Cycling Switch Replacement . Is the repair complete? | -- | Go to HVAC System Check | --
11 | Backprobe the A/C compressor clutch relay connector with a test lamp from cavity 1 to chassis ground. Does the test lamp light? | -- | Go to Step 13 | Go to Step 12
12 | Repair the open in the YEL wire between the refrigerant pressure switch and the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
13 |

1. Turn the ignition switch to LOCK.
2. Disconnect the A/C compressor clutch relay connector.
3. Disconnect the A/C compressor control module connector.
4. Connect a digital multimeter from cavity 3 of the A/C compressor clutch relay connector to cavity 7 of the A/C compressor control module connector.
5. Measure the resistance.

Is the resistance less than the specified value?

0.5 ohms

Go to Step 15

Go to Step 14

14 | Repair the open in the PNK wire between the A/C compressor clutch relay and the A/C compressor control module. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
15 |

1. Connect the A/C compressor clutch relay connector.
2. Turn the ignition switch to ON.
3. Connect a fused jumper wire from the A/C compressor control module connector cavity 7 to chassis ground.

Does the A/C compressor clutch relay energize?

--

Go to Step 17

Go to Step 16

16 | Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement . Is the repair complete? | -- | Go to HVAC System Check | --
17 |

1. Connect a digital multimeter from the A/C compressor control module connector cavity 9 to chassis ground.
2. Measure the resistance.

Is the resistance less than the specified value?

3 ohms

Go to Step 19

Go to Step 18

18 | Repair the open in the BLK wire between G202 and the A/C compressor control module. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
19 |

1. Turn the ignition switch to ON.
2. Turn the blower switch to any position except OFF.
3. Turn the A/C switch to ON.
4. Backprobe the A/C compressor control module connector with a test lamp from cavity 11 to chassis ground.

Does the test lamp light?

--

Go to Step 29

Go to Step 20

20 |

1. Turn the ignition switch to ON.
2. Turn the blower switch to any position except OFF.
3. Turn the A/C switch to ON.
4. Backprobe the A/C switch connector with a test lamp from cavity 2 to chassis ground.

Does the test lamp light?

--

Go to Step 21

Go to Step 22

21 | Repair the open in the BLU wire between the A/C compressor control module and the A/C switch. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
22 |

1. Turn the ignition switch to ON.
2. Turn the blower switch to any position except OFF.
3. Backprobe the A/C switch connector with a test lamp from cavity 1 to chassis ground.

Does the test lamp light?

--

Go to Step 23

Go to Step 24

23 | Replace the A/C switch. Refer to Control Assembly Replacement . Is the repair complete? | -- | Go to HVAC System Check | --
24 |

1. Turn the ignition switch to ON.
2. Turn the blower switch to any position except OFF.
3. Backprobe the blower speed selector switch connector with a test lamp from cavity 4 to chassis ground.

Does the test lamp light?

--

Go to Step 25

Go to Step 26

25 | Repair the open in the PNK/BLK wire between the blower speed selector switch and the A/C switch. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
26 |

1. Turn the ignition switch to ON.
2. Backprobe the blower speed selector switch connector with a test lamp from cavity 1 to chassis ground.

Does the test lamp light?

--

Go to Step 28

Go to Step 27

27 | Repair the open in the LT GRN wire between the blower speed selector switch and fuse block 2. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
28 | Replace the blower speed selector switch. Refer to Blower Switch Replacement . Is the repair complete? | -- | Go to HVAC System Check | --
29 |

1. Probe the A/C compressor control module connector with a digital multimeter from cavity 12 to chassis ground.
2. Measure the resistance.

Is the resistance less than the specified value?

5 ohms

Go to Step 33

Go to Step 30

30 |

1. Backprobe the engine coolant temperature (ECT) switch connector with a digital multimeter from the connector cavity to ground.
2. Measure the resistance.

Is the resistance less than the specified value?

5 ohms

Go to Step 32

Go to Step 31

31 | Replace the ECT switch. Refer to Engine Coolant Temperature Sensor Replacement in Engine Controls. Is the repair complete? | -- | Go to HVAC System Check | --
32 | Repair the open in the YEL/BLU wire between the ECT switch and the A/C compressor control module. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
33 |

1. Probe the A/C compressor control module connector with a digital multimeter from cavity 10 to cavity 4.
2. Measure the resistance.

Is the resistance less than the specified value?

2K ohms

Go to Step 34

Go to Step 35

34 | Replace the A/C compressor control module. Refer to Air Conditioning (A/C) Compressor Control Module Replacement . Is the repair complete? | -- | Go to HVAC System Check | --
35 |

1. Disconnect the evaporator temperature sensor connector.
2. Probe the evaporator temperature sensor connector with a digital multimeter from cavity 2 to cavity 10 of the A/C compressor control module connector.
3. Measure the resistance.

Is the resistance less than the specified value?

5 ohms

Go to Step 37

Go to Step 36

36 | Repair the open in the YEL/RED wire between the A/C compressor control module and the evaporator temperature sensor. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
37 |

1. Probe the A/C compressor control module connector with a digital multimeter from cavity 4 to the evaporator temperature sensor connector cavity 1.
2. Measure the resistance.

Is the resistance less than the specified value?

5 ohms

Go to Step 39

Go to Step 38

38 | Repair the open in the WHT/BLU wire between the A/C compressor control module and the evaporator temperature sensor. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to HVAC System Check | --
39 | Replace the evaporator temperature sensor. Refer to Air Conditioning (A/C) Temperature Sensor Replacement . Is the repair complete? | -- | Go to HVAC System Check | --
40 | Replace the A/C compressor clutch. Refer to Air Conditioning Compressor Replacement . Is the repair complete? | -- | Go to HVAC System Check | --

#### Compressor Control Module Voltage Table

Terminal/Wire | Circuit | Normal Value | Condition
--- | --- | --- | ---
1/YEL/BLK | Idle up control | 10-14 Volts | Ignition switch ON
0-1 Volt | Blower, A/C and ignition switch ON
2-3 | Not used
4/WHT/BLU | Evaporator temperature input | 1.2-1.5 Volts (2107-2575ohms) | Evaporator temperature approximately 15°C (59°F) with ignition switch ON
2.1-2.4 Volts (4609-5095ohms | Evaporator temperature approximately 0°C (32°F) with ignition switch ON
5 | Not used
6/BLU/RED | Condenser fan relay control | 10-14 Volts | Ignition switch ON
0-1 Volt | Blower, A/C and ignition switch ON or engine coolant temperature greater than 113°C (235°F) with ignition switch ON
7/PNK | Compressor clutch relay control | 10-14 Volts | Ignition switch ON
0-1 Volt | Blower, A/C and ignition switch ON
8/LT GRN | Ignition positive voltage | 10-14 Volts | Ignition switch ON
9/BLK | Ground | 0-1 Volt | Ignition switch ON
10/YEL/RED | Evaporator temperature sensor ground | 0-1 Volt | Ignition switch ON
11/BLU | A/C request signal | 10-14 Volts | Blower, A/C and ignition switch ON
0-1 Volt | Ignition switch ON
12/YEL/BLU | Engine coolant temperature (ECT) sensor signal | 0-1 Volt | Engine coolant temperature less than 110°C (230°F) with ignition switch ON
10-14 Volts | Engine coolant temperature greater than 113°C (235°F) with ignition switch ON