GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 DeVille 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 HVAC Compressor Clutch Does Not Engage

Circuit Description

The compressor clutch coil is fed power through the A/C relay. The coil is grounded through CKT 350.

Test Description

  1. Before you begin to diagnose the problem, correct and clear all DTCs. An open power steering switch or a faulty throttle position sensor may prevent the A/C clutch from engaging.

    2.

  2. This step determines whether the A/C relay is receiving power on CKT 2340.

    3.

  3. This step determines whether the compressor clutch is faulty. Test for an open in ground CKT 350.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2
  1. Verify that the A/C system pressures are normal.
  2. Idle the engine at the normal operating temperature.
  3. Turn the A/C off.

Is the A/C clutch engaged?

--

Go to Step 3

Go to Step 10

3

With the engine idling, connect a Scan Tool .

Does the Scan Tool display the A/C request NO?

--

Go to Step 4

Go to Step 5

4

Refer to Powertrain Control Power and Ground Check in Engine Controls - 4.0, 4.6L.

Did you complete the repair?

--

Go to Diagnostic System Check

--

5

Verify the following Scan Tool readings:

  1. The OUTSIDE TEMP is close to the ambient temperature if the car is moving at highway speeds.
  2. The EVAP INLET TEMP is above the specified value.

Do the sensors read OK?

-12°C

(10°F)

Go to Step 6

Go to Step 7

6

Replace the heater and A/C programmer. Refer to Programmer Replacement .

Did you complete the repair?

--

Go to Diagnostic System Check

--

7

Test for additional resistance in the sensor wiring caused by a loose or corroded connection.

Is the sensor wiring OK?

--

Go to Step 8

Go to Step 9

8

Replace the sensor. Refer to Ambient Temperature Sensor Replacement .

Did you complete the repair?

--

Go to Diagnostic System Check

--

9

Repair the faulty sensor wiring. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Diagnostic System Check

--

10
  1. Connect the Scan Tool .
  2. Command A/C ON/OFF.
  3. Turn the A/C ON.

Does the A/C relay cycle?

--

Go to Step 19

Go to Step 11

11
  1. Remove the A/C relay.
  2. Measure the coil resistance on relay pin C3 and pin D1.

Is the coil resistance within the specified values?

70 ohms -150 ohms

Go to Step 12

Go to Step 15

12

Measure the voltage between harness pin C3 and ground.

Is the voltage within the specified range?

10 -15 V

Go to Step 13

Go to Step 14

13

Repair the open in the following components:

    • CKT 604
    • CKT 603
    • CKT 339 Fuse
    • The A/C low pressure switch
    • The A/C high pressure switch

Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Diagnostic System Check

--

14

Repair the open in CKT 339. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Diagnostic System Check

GO to Powertrain Control Power and Ground Check in Engine Controls - 4.0, 4.6L.

15

Is the coil resistance greater than the specified value?

150 ohms

Go to Step 16

Go to Step 17

16

Replace the relay.

Did you complete the repair?

--

Go to Diagnostic System Check

--

17

Is the coil resistance less than the specified value?

70 ohms

Go to Step 18

--

18

Replace the A/C relay.

Did you complete the repair?

--

Go to Diagnostic System Check

--

19
  1. Remove the A/C relay.
  2. Move the fused jumper from pin D3 to pin C1.

Does the clutch engage?

--

Go to Step 20

Go to Step 21

20

Replace the A/C relay.

Did you complete the repair?

--

Go to Diagnostic System Check

--

21

Move the fused jumper from pin D1 to pin C1.

Does the clutch engage?

--

Go to Step 22

Go to Step 23

22
  1. Repair the open in CKT 2340 or replace the A/C compressor fuse. Refer to Wiring Repairs in Wiring Systems.
  2. If the fuse is blown, test for a short to ground.

Did you complete the repair?

--

Go to Diagnostic System Check

--

23

With the jumper still connected, measure the voltage at pin A of the compressor clutch.

Is the voltage equal to the battery voltage?

B+

Go to Step 25

Go to Step 24

24

Repair the open in CKT 59. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Diagnostic System Check

--

25

Test the continuity between pin B of the compressor clutch connectors and ground.

Is there continuity?

--

Go to Step 26

Go to Step 29

26

Test the A/C compressor clutch coil diode for a short.

Is there a short?

--

Go to Step 27

Go to Step 28

27

Repair the short in the A/C compressor clutch coil diode. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Diagnostic System Check

--

28

Replace the compressor clutch coil. Refer to Air Conditioning Clutch Coil Removal .

Did you complete the repair?

--

Go to Diagnostic System Check

--

29

Repair the open in CKT 350. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Diagnostic System Check

--