The following chart will help you to diagnose V7 compressor and VDOT refrigerant system problems that cause insufficient cooling. Use the chart in conjunction with other appropriate service manual information.
The V7 compressor is a variable displacement compressor. The compressor matches air conditioning demand by changing stroke instead of cycling the clutch. A control valve that is located in the rear head of the compressor senses compressor low side pressure. The valve then causes the compressor mechanism to change stroke. These diagnostic procedures differ from those used for fixed displacement systems because the V7 compressor always runs and the system does not cycle. Use these procedures in order to avoid needlessly replacing A/C components.
If the discharge air temperature with the A/C is normal after you make the following repairs, then the system operates properly. Repair the following components as necessary:
| • | The A/C fuse |
| • | The A/C blower operation |
| Refer to Blower Motor and Fan Replacement . |
| • | The clutch coil and the rear head switch(es) connections |
| • | The compressor belt |
| Adjust or replace the belt if the belt is damaged or missing. |
| • | Engine cooling fan operation |
| Refer to Fan in Engine Cooling. |
| • | Inspect the condenser for restricted air flow. |
Step | Action | Value(s) | Yes | No | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 |
Important: Before you proceed with this step, perform the following steps:
Turn OFF the ignition key. Connect a high pressure gauge and a low pressure gauge. Ensure that the pressures are approximately equal. Are both pressures above 50 psi (345 kPa)? | -- | Go to Step 8 | Go to Step 2 | ||||||||||
2 | Are both pressures below 10 psi (69 kPa)? | -- | Go to Step 3 | Go to Step 5 | ||||||||||
3 | Add 1 lb of R-134a. Inspect the system for leaks. Did you find a leak? | -- | Go to Step 4 | System OK | ||||||||||
4 | Repair the leak. Recover the system. Evacuate the system. Charge the system. Refer to Refrigerant Recovery and Recharging . Is the repair complete? | -- | System OK | -- | ||||||||||
5 | Are both pressures within 10-50 psi (69-345 kPa)? | -- | Go to Step 6 | Go to Step 8 | ||||||||||
6 | Inspect the system. Add R-134a if necessary. Is a leak found? | -- | Go to Step 7 | System OK | ||||||||||
7 | Repair the leak. Recover the system. Evacuate the system. Charge the system. Refer to Refrigerant Recovery and Recharging . Is the repair complete? | -- | System OK | -- | ||||||||||
8 | Run the engine at idle. Set the A/C controls to the following settings:
Did the clutch engage? | -- | Go to Step 13 | Go to Step 9 | ||||||||||
9 |
Did the clutch engage? | -- | Go to Step 11 | Go to Step 10 | ||||||||||
10 | Replace the clutch coil. Is the repair complete? | -- | System OK | -- | ||||||||||
11 | Repair the electrical circuit to the compressor clutch. Is the repair complete? | -- | Go to Step 12 | -- | ||||||||||
12 | Run the engine at idle. Set the A/C controls to the following settings:
Did the clutch engage? | -- | System OK | -- | ||||||||||
13 | Do you hear a loud underhood knocking noise from the compressor and/or did the belt slip? | -- | Go to Step 14 | Go to Step 15 | ||||||||||
14 | Recover the system. Refer to Refrigerant Recovery and Recharging . Replace the compressor. Refer to Air Conditioning Compressor Replacement . Is the repair complete? | -- | Go to Step 15 | -- | ||||||||||
15 | Evacuate the system. Charge the system. Refer to Refrigerant Recovery and Recharging Perform a leak test. Refer to Leak Testing . Is a leak detected? | -- | Go to Step 16 | Go to Step 17 | ||||||||||
16 | Repair the leak. Is the repair complete? | -- | Go to Step 17 | -- | ||||||||||
17 |
Important: This test is designed for the following typical garage conditions:
Do you feel a temperature difference? | -- | Go to Step 18 | Go to Step 19 | ||||||||||
18 |
Did you locate the intersection? | -- | Go to Step 24 | -- | ||||||||||
19 | Recover the system. Refer to Refrigerant Recovery and Recharging . Inspect the system. Is the orifice (expansion) tube missing? | -- | Go to Step 20 | -- | ||||||||||
20 | Install an orifice (expansion) tube. Is the repair complete? | -- | Go to Step 21 | -- | ||||||||||
21 | Evacuate the system. Charge the system. Refer to Refrigerant Recovery and Recharging . Perform a leak test. Refer to Leak Testing . Did you detect a leak? | -- | Go to Step 22 | Go to Step 23 | ||||||||||
22 | Repair the leak. Is the repair complete? | -- | Go to Step 23 | -- | ||||||||||
23 | Note the discharge air temperature. Is the discharge air temperature within specifications? | -- | -- | Go to Step 17 | ||||||||||
24 | Refer to Low and High Side Pressure Relationship Chart . Do the high and low side pressures intersect in the white area of the chart? | -- | System OK. | Go to Step 25 | ||||||||||
25 | Refer to Low and High Side Pressure Relationship Chart . Do the high and low side pressures intersect in the gray area of the chart? | -- | Go to Step 27 | Go to Step 26 | ||||||||||
26 | Refer to Low and High Side Pressure Relationship Chart . Do the high and low side pressures intersect in the striped area of the chart? | -- | Go to Step 33 | -- | ||||||||||
27 |
Is the tube cold? | -- | Go to Step 28 | Go to Step 29 | ||||||||||
28 | Inspect for a restriction in the high side. Recover the system. Refer to Refrigerant Recovery and Recharging . Remove any restrictions. Is the repair complete? | -- | Go to Step 32 | -- | ||||||||||
29 | Inspect the system for refrigerant overcharge or air in the system. Did you detect a condition? | -- | Go to Step 30 | -- | ||||||||||
30 | Recover the system. Refer to Refrigerant Recovery and Recharging . Is the procedure complete? | -- | Go to Step 31 | -- | ||||||||||
31 | Evacuate the system. Charge the system. Refer to Refrigerant Recovery and Recharging . Perform a leak test. Refer to Leak Testing . Did you detect a leak? | -- | Go to Step 32 | -- | ||||||||||
32 | Repair any leaks. Is the repair complete? | -- | Go to Step 17 | -- | ||||||||||
33 | Are the compressor high and low side pressures within 206.8 kPa (30 psi) of each other? | -- | Go to Step 38 | Go to Step 34 | ||||||||||
34 | Is the low side pressure within the specified range? | 172.4-241.3 kPa (25-35 psi) | Go to Step 35 | Go to Step 43 | ||||||||||
35 | The refrigerant is undercharged. Add .396 kg (14 oz) of refrigerant to the system. Does the cooling performance improve? | -- | Go to Step 41 | Go to Step 36 | ||||||||||
36 |
Is the tube plugged? | -- | Go to Step 37 | Go to Step 38 | ||||||||||
37 | Clear the tube lines. Replace the orifice (expansion) tube. If there is only a light debris, clean the tube with compressed air. Is the repair complete? | -- | Go to Step 41 | -- | ||||||||||
38 |
Are the compressor high and low side pressures within 206.8 kPa (30 psi) of each other? | Go to Step 39 | Go to Step 17 | |||||||||||
39 | Turn OFF the engine. Ensure that the compressor clutch is disengaged. Does the compressor clutch driver (not the pulley) turn freely when spun by hand? | -- | Go to Step 40 | Go to Step 43 | ||||||||||
40 | Replace the compressor. Refer to Air Conditioning Compressor Replacement . Is the repair complete? | -- | Go to Step 41 | -- | ||||||||||
41 | Evacuate the system. Charge the system. Perform a leak test. Did you detect a leak? | -- | Go to Step 42 | Go to Step 17 | ||||||||||
42 | Repair the leak. Is the repair complete? | -- | Go to Step 17 | -- | ||||||||||
43 |
Important: Follow this test procedure exactly. The test is designed to create a low cooling load in order to cause the V7 compressor to operate at less than full stroke. This is necessary for accurate test results.
Is the low side pressure within the specified range? | 172.4-241.3 kPa (25-35 psi) | Go to Step 17 | Go to Step 44 | ||||||||||
44 | Recover the system. Refer to Refrigerant Recovery and Recharging Replace the control valve. Is the repair complete? | -- | Go to Step 45 | -- | ||||||||||
45 | Evacuate the system. Charge the system. Refer to Refrigerant Recovery and Recharging Perform a leak test. Refer to Leak Testing . Did you detect a leak? | -- | Go to Step 46 | Go to Step 17 | ||||||||||
46 | Repair the leak. Is the repair complete? | -- | Go to Step 17 | -- |
