The purpose of the symptom diagnostic procedures is to diagnose the following components for any problems that may cause insufficient cooling:
| • | The V5 compressor |
| • | The VDOT refrigerant system |
The V5 Compressor is a variable displacement compressor. The V5 compressor responds to the air conditioning demands by changing the stroke rather that cycling the clutch. A control valve is located in the rear head of the A/C compressor. The control valve completes the following functions; senses the compressor low side pressure and causes the compressor mechanism to stroke. The V5 compressor always runs and the system does not cycle. These diagnostic procedures differ from those used for fixed displacement systems. Use the symptom diagnostic procedures in order to avoid unnecessary replacement of any A/C components.
Preliminary Checks
| • | Inspect the A/C fuse, replace as necessary. |
| • | Inspect the A/C blower operation, repair as necessary. |
| • | Inspect the clutch coil electrical connection, repair as necessary. |
| • | Check for diagnostic codes, repair as necessary. |
| • | Inspect the drive belt, replace the drive belt if it is damaged. |
| • | Inspect the operation of the electric cooling fans, repair as necessary. |
| • | Inspect the condenser for restricted air flow, clean as necessary. |
| • | Inspect the system for any restrictions in the air flow. |
The A/c system is operating properly if the discharge air temperature and compressor pressures are equal to those in the System Performance Test
Low Side and High Side Pressure Chart
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Were you sent here from the VDOT System Performance Test? | -- | Go to Step 2 | Go to System Performance Test |
2 |
Are the high and low side pressures approximately equal to the value specified? | 345 kPa (50 psi) | Go to Step 7 | Go to Step 3 |
3 | Add 0.5 kg (1 lb of R-134a) Inspect the A/C system for leaks. Refer to Leak Testing Is there a leak? | -- | Go to Step 5 | Go to Step 4 |
4 | Are the high and low side pressures within the specified range? | 207-345 kpa (30-50 psi) | System OK | Go to Step 5 |
5 | Repair the leak. Is the repair complete? | -- | Go to Step 6 | -- |
6 | Evacuate and charge the A/C system. Refer to Refrigerant Recovery and Recharging Are the high and low side pressures above the value specified? | 345 kpa (50 psi) | System OK | Go to Step 7 |
7 |
Dose the clutch engage? | -- | Go to Step 8 | Go to Step 16 |
8 | Check for noise coming from the compressor or the A/C drive belt area. Is the noise coming from the compressor or the belt? | -- | Go to Step 9 | Go to Step 19 |
9 | Inspect the belt for slippage. Is the noise due to belt slippage? | -- | Go to Step 10 | Go to Step 11 |
10 | Replace the accessory drive belt. Refer to Drive Belt Replacement Is the repair complete? | -- | System OK | Go to Step 14 |
11 | Listen to the A/C compressor for the noise. Is the noise coming from the A/C compressor? | -- | Go to Step 12 | Go to Step 14 |
12 | Check the A/C lines for contact with other components. Is there contact with other components? | -- | Go to Step 13 | Go to Step 14 |
13 | Reposition or replace the A/C lines as necessary. Is the repair complete? | -- | System OK | Go to Step 19 |
14 | Is the noise coming from the A/C compressor? | -- | Go to Step 15 | Go to Step 19 |
15 | Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement Is the noise still present? | -- | Go to Step 19 | System OK |
16 |
Dose the clutch engage? | -- | Go to Step 17 | Go to Step 18 |
17 |
Dose the clutch engage? | -- | System OK | Go to Step 19 |
18 | Replace the A/C clutch coil. Air Conditioning Clutch Coil Removal Is the repair complete? | -- | System OK | Go to Step 19 |
19 |
Is the temperature the same on both sides of the expansion (orifice) tube (C60) or two stage orifice (CJ4)? | -- | Go to Step 20 | Go to Step 25 |
20 |
Is the expansion (orifice) tube or O-ring missing? | -- | Go to Step 21 | Go to Step 22 |
21 | Replace the missing expansion (orifice) tube or O-ring (C60). Refer to Expansion (Orifice) Tube Replacement Replace the two stage orifice (CJ4). Refer to Two Stage Orifice Replacement Is the repair complete? | -- | Go to Step 23 | -- |
22 | Inspect for a restricting in the high side line; visually check the line/pipe for a frosty spot or phyically check the line/pipe for a temperature difference to locate the restriction. Is there a restriction? | -- | Go to Step 24 | -- |
23 |
Is the air outlet discharge temperature within specifications? | -- | System OK | Go to Step 25 |
24 | Repair the restriction in the high side line. Is the repair done? | -- | System OK | -- |
25 |
Do the low and high side pressures intersect on the right side of the chart? | -- | Go to Step 26 | Go to Step 36 |
26 |
Set the temperature to full cold. Is the liquid line cold? | -- | Go to Step 27 | Go to Step 31 |
27 | Check the cooling fan(s). Are the fans operating? | -- | Go to Step 28 | Go to Step 29 |
28 | Check the air flow at the condenser for restrictions. Is the air flow restricted? | -- | Go to Step 30 | Go to System Performance Test |
29 | Repair the cooling fan(s) as necessary. Is the repair complete? | -- | System OK | -- |
30 | Remove the restriction. Is the repair complete? | -- | System OK | -- |
31 | Check the A/C system for an overcharge of refrigerant. Is the A/C system overcharged? | -- | Go to Step 32 | Go to Step 33 |
32 | Recover the refrigerant. Refer to Refrigerant Recovery and Recharging Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging Is the repair complete? | -- | System OK | Go to System Performance Test |
33 | Check for air in the A/C system. Is there a leak in the A/C system? | -- | Go to Step 34 | Go to System Performance Test |
34 | Leak test the A/C system. Refer to Leak Testing Is there a leak in the A/C system. | -- | Go to Step 35 | Go to System Performance Test |
35 |
Is the repair complete? | -- | System OK | -- |
36 | With the engine running, connect the high and low side pressure gages. Are the high and low side pressures equal to the specified value? | 207 kpa (30 psi) | Go to Step 37 | Go to Step 42 |
37 |
Are the high and low side pressures equal the specified value? | 207 kpa (30 psi) | Go to Step 38 | -- |
38 | Inspect for the following conditions:
Do all of the above conditions exist? | -- | Go to Step 39 | Go to Step 40 |
39 | Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement Is the repair complete? | -- | System OK | -- |
40 | Turn the engine OFF. With the compressor clutch disengaged, does the compressor clutch driver (not the pulley) turn freely by hand? | -- | Go to Step 39 | Go to Step 41 |
41 | Inspect the low side pressure. Is there a rapid rise in the low side pressure with the engine RPM between the value(s) shown? | 2000-2800 RPM | Go to Step 52 | Go to Step 39 |
42 | Inspect the low side pressure. Is the low side pressure within the specified values? | 172-241 kpa (27-38 psi) | Go to Step 43 | Go to Step 52 |
43 | Feel the liquid line before the expansion (orifice) tube (C60) or two stage orifice (CJ4). Is the line cold? | -- | Go to Step 44 | Go to Step 46 |
44 | Inspect the liquid line for a restriction before the expansion (orifice) tube (C60) or two stage orifice (CJ4). Is there a restriction in the liquid line? | -- | Go to Step 45 | Go to System Performance Test |
45 | Repair the restriction or replace the liquid line before the expansion (orifice) tube (C60) or two stage orifice (CJ4). Is the repair complete? | -- | System OK | Go to System Performance Test |
46 | Add 0.5 kg (1 lb) of R--134a refrigerant to the system. Does the cooling improve? | -- | Go to Step 47 | Go to Step 49 |
47 | Preform a leak test. Refer to Leak Testing Is there a leak? | -- | Go to Step 48 | System OK |
48 |
Is the repair complete? | -- | System OK | -- |
49 |
Is the expansion (orifice) tube (C60) or two stage orifice (CJ4) plugged? | -- | Go to Step 50 | -- |
50 | Remove and clean or replace the expansion (orifice) tube (C60). Refer to Expansion (Orifice) Tube Replacement . Relpace the two stage orifice (CJ4). Refer to Two Stage Orifice Replacement . Is the repair complete? | -- | Go to Step 51 | -- |
51 | Evacuate and charge the A/C system. Refer to Refrigerant Recovery and Recharging Is the repair complete? | -- | System OK | Go to System Performance Test |
52 |
Is the low side pressure within the value (s) shown? | 172-241 kpa (25-35 psi) | Go to System Performance Test | Go to Step 53 |
53 |
Is the repair complete? | -- | Go to Step 54 | -- |
54 | Evacuate and charge the A/C system. Refer to Refrigerant Recovery and Recharging Is the repair complete? | -- | System OK | Go to System Performance Test |
