V5 A/C System (Manual Control Type) Description
The V5 variable displacement compressor along with the thermal expansion valve on the evaporator, constitutes a largely self-regulating system. There is no pressure cycling switch, no high-pressure cut-off switch and no low-pressure cut-off switch. The compressor clutch is controlled by the engine control module (ECM), which receives data from various engine systems and from a pressure transducer located in the high-pressure refrigerant pipe. In normal operation, the clutch is engaged continuously. Should one of the monitored conditions become abnormal, the ECM will disengage the compressor clutch until normal operation is restored. These conditions include the following
- Wide-open throttle.
- High engine coolant temperature.
- High engine RPM.
- Refrigerant low pressure.
- Refrigerant high pressure.
The compressor clutch will remain disengaged until normal operation is established.
V5 Compressor-General Description
Vehicles using the V5 compressor may have differences between installations in the mounting brackets, the drive systems, the pulleys, the connections and the system capacities. Basic overhaul procedures are similar between the compressors used on different vehicles.
When servicing the compressor, keep dirt and foreign material from getting on or into the compressor parts and the system. Clean tools and a clean work area are important for proper service. The compressor connections and the outside of the compressor should be cleaned before undertaking any on-vehicle repairs and before the removal of the compressor. The parts must be kept clean at all times. Any parts that are to be reassembled should be cleaned with trichloroethane, naphtha, stoddard solvent, kerosene or equivalent solvents and dried with dry air. Use only lint-free cloths to wipe the parts.
The operations described are based on bench overhaul with the compressor removed from the vehicle, except as noted. They have been prepared in the order of accessibility of the components. When a compressor is removed from the vehicle for servicing, the amount of oil remaining in the compressor should be drained, measured and recorded. This oil should then be discarded and new polyalkaline glycol (PAG) refrigerant oil added to the compressor.
Note. The oil drain plug must be removed and the oil drained through the plug opening to insure complete draining of the oil from the compressor.
V5 Compressor-Description of Operation
The V5 is a variable displacement compressor that can match the automotive A/C demand under all conditions without cycling. The basic compressor mechanism is a variable angle wobble-plate with 5 axially oriented cylinders. The center of control of the compressor displacement is a billows-actuated control valve located in the rear head of the compressor that senses compressor suction pressure.
The wobble-plate angle and the compressor displacement are controlled by the crankcase suction pressure differential. When the A/C capacity demand is high, the suction pressure will be above the control point. The valve will maintain a bleed from crankcase to suction. With no crankcase-suction pressure differential, the compressor will have maximum displacement.
When the A/C capacity demand is lower and the suction pressure reaches the control point, the valve will bleed discharge gas into the crankcase and close off a passage from the crankcase to the suction plenum. The angle of the wobble-plate is controlled by a force balance on the 5 pistons. A slight elevation of the crankcase suction pressure differential creates total force on the pistons resulting in a movement about the wobble-plate pivot pin that reduces the plate angle.
The compressor has a unique lubrication system. The crankcase suction bleed is routed through the rotating wobble-plate for lubrication of the wobble-plate bearing. The rotation acts as an oil separator which removes some of the oil from the crankcase suction bleed, re-routing it to the crankcase where it can lubricate the compressor mechanism.
Scheme 27
Scheme 28
Test Description
The numbers below refer to steps on the diagnostic table.
- 13. See the CAUTION below. CAUTION: Perform this test under garage conditions with the air temperature at 21 - 32 °C (70 - 90 °F), and no sun load. Follow this test carefully for accurate results.
- 32. See the CAUTION below. CAUTION: Perform this test exactly as described to obtain accurate results.
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| 1 | Record the customer's complaint. Can you verify the customer's complaint? | Go to Step 2 | System OK | |
| 2 | Check the A/C fuse. Check the blower fan operation. Check the engine cooling fan operation. Check the A/C compressor belt. Check the A/C condenser for restricted airflow. Check the clutch coil connection. Repair or replace any components as needed. Check the discharge air temperature with the A/C turned ON. Is the discharge air temperature normal? | At least 7 °C (44.6 °F) below ambient air temperature | System OK | Go to Step 3 |
| 3 | Turn the ignition switch to LOCK. Connect the high- and the low-pressure gauges. Are both pressures within the value specified? | 69 - 345 kPa (10 - 50 psi) | Go to Step 4 | Go to Step 5 |
| 4 | Check the A/C system for leaks. Repair any refrigerant leaks as needed. Recover, evacuate and recharge the A/C system. Observe the 2 pressure gauges. Are both pressures above the value specified? | 345 kPa (50 psi) | Go to Step 7 | |
| 5 | Observe the 2 pressure gauges. Are both pressures below the value specified? | 69 kPa (10 psi) | Go to Step 6 | Go to Step 7 |
| 6 | Add 0.45 kg (1 pound) of refrigerant R-134a. Check the A/C system for leaks. Repair any refrigerant leaks, as needed. Recover, evacuate and recharge the A/C system. Observe the 2 pressure gauges. Are both pressures above the value specified? | 345 kPa (50 psi) | Go to Step 7 | |
| 7 | Start the engine and allow it to run at idle. Set the A/C controls to the following positions: The A/C switch to the ON. The fresh air control switch to fresh air (indicator lamp OFF). The blower motor to 4. The temperature to full cold. Does the A/C compressor clutch engage? | Go to Step 8 | Go to Step 10 | |
| 8 | Check for a knocking noise from the A/C compressor. Cycle the A/C compressor ON and OFF in order to verify the source of the noise. Do you hear a loud knocking noise? | Go to Step 9 | Go to Step 13 | |
| 9 | Recover the A/C system refrigerant. Replace the A/C compressor. Evacuate and recharge the A/C system. Check the A/C system for leaks. Is the compressor running normally? | Go to Step 13 | ||
| 10 | Turn the ignition switch to LOCK. Disconnect the A/C compressor clutch coil connector. Connect a jumper wire from ground to one A/C compressor clutch coil terminal. Connect a fused jumper wire from the positive battery terminal to the other A/C compressor clutch coil terminal. Does the A/C clutch engage? | Go to Step 11 | Go to Step 12 | |
| 11 | Repair the electrical circuit to the A/C compressor clutch coil. Does the A/C clutch engage? | Go to Step 8 | ||
| 12 | Replace the A/C compressor clutch coil. Does the A/C clutch engage? | Go to Step 8 | ||
| 13 | Close all of the vehicle's windows and doors. Set the A/C controls to the following positions: The A/C switch to the ON position. The fresh air control switch to fresh air. The blower motor to 4. The temperature to full cold. Start the engine and allow it to run at idle for 5 minutes. Feel the evaporator inlet and outlet pipes. Is there a noticeable difference in the temperature of the evaporator inlet and outlet pipes? | Go to Step 15 | Go to Step 14 | |
| 14 | Turn the ignition switch to LOCK. Recover the A/C system refrigerant. Examine the high-pressure pipe for an obstruction. Examine the expansion valve for an obstruction or a malfunction. Repair the obstruction or replace the expansion valve as needed. Evacuate and recharge the A/C system. Check the A/C system for leaks. Note the discharge air temperature with the A/C ON. Is the discharge temperature normal? | At least 7 °C (44.6 °F) below ambient air temperature | Go to Step 15 | Go to Step 13 |
| 15 | Record the low- and the high-side pressures after the A/C system has been operating for 5 minutes or more with the engine cooling fan ON. Locate the intersection of the low- and the high-side pressures. Refer to Handling Refrigerant . Do the low- and the high-side pressures intersect in the white area of the chart? | System OK | Go to Step 16 | |
| 16 | Check the high- and the low-side pressures. Do the low- and the high-side pressures intersect in the gray area of the chart? | Go to Step 17 | Go to Step 20 | |
| 17 | Feel the liquid pipe between the condenser and the expansion valve. Is the pipe cold? | Go to Step 18 | Go to Step 19 | |
| 18 | Examine the condenser for any restriction of the airflow. Check the cooling fans for proper operation. Remove the restriction or repair the fans, as required. Is the pipe temperature normal now? | At least 7 °C (44.6 °F) below ambient air temperature | Go to Step 13 | |
| 19 | Recover, evacuate and recharge the A/C system. Check the A/C system for leaks. Is the system free from leaks? | Go to Step 13 | ||
| 20 | Observe the readings on the pressure gauges. Are the A/C compressor high- and low-side pressures within the specified value of each other? | 207 kPa (30 psi) | Go to Step 21 | Go to Step 26 |
| 21 | Run the engine at 3,000 rpm. Set the A/C controls to the following positions: The A/C switch to the ON. The fresh air control switch to fresh air. The blower motor to 4. The temperature to full cold. Close all of the vehicle's windows and doors. Turn the A/C switch ON and OFF every 20 seconds for 3 minutes. Are the A/C compressor high- and low-side pressures within the specified value of each other? | 207 kPa (30 psi) | Go to Step 22 | Go to Step 13 |
| 22 | Observe the pressure rise on both gauges and the temperatures of both the compressor suction pipe and the discharge pipe. Is the pressure rise on both gauges slow and the suction pipe warm with the discharge pipe very hot? | Go to Step 25 | Go to Step 23 | |
| 23 | Turn the ignition switch to LOCK. Make sure the compressor clutch is disengaged. Attempt to turn the clutch driver (not the pulley). Can you turn the clutch driver freely by hand? | Go to Step 25 | Go to Step 24 | |
| 24 | Start the engine. Observe the low-side pressure gauge while running the engine between 3,000 and 3,800 rpm. Does the low-side pressure rise rapidly? | Go to Step 32 | Go to Step 25 | |
| 25 | Recover the A/C system refrigerant. Replace the A/C compressor. Evacuate and recharge the A/C system. Is the compressor functioning normally? | Go to Step 13 | ||
| 26 | Check the low-side pressure. Is the low-side pressure within the specified value? | 172 - 241 kPa (27 - 38 psi) | Go to Step 27 | Go to Step 32 |
| 27 | Feel the high-side pipe leading up to the expansion valve connecting block. Is the pipe cold before the connecting block? | Go to Step 28 | Go to Step 29 | |
| 28 | Check for a restriction in the high-side pipe before the expansion valve. Repair or replace the high-side pipe. Is the pipe performing normally? | Go to Step 13 | ||
| 29 | Add the specified amount of refrigerant to the A/C system. Does the cooling performance improve? | 0.40 kg (14 ounces) | Go to Step 30 | Go to Step 31 |
| 30 | Check the A/C system for leaks. Repair any refrigerant leaks, as needed. Evacuate and recharge the A/C system. Check the A/C system for leaks. Is the system free from leaks? | Go to Step 13 | ||
| 31 | Recover the refrigerant. Check the expansion valve for obstructions. Repair or replace the expansion valve, as required. Evacuate and recharge the system. Check the A/C system for leaks. Is the system free from leaks? | Go to Step 13 | ||
| 32 | Run the engine for 5 minutes at 2,000 rpm. Set the A/C controls to the following positions: The A/C switch to the ON position. The fresh air control switch to recirculate (indicator lamp ON). The blower motor to 1. The temperature to full cold. Close all of the vehicle's windows and doors. Open the vehicle hood. Is the low-side pressure within the specified value? | 172 - 241 kPa (25 - 35 psi) | Go to Step 13 | Go to Step 33 |
| 33 | Recover the A/C system refrigerant. Replace the A/C compressor control valve. Evacuate and recharge the A/C system. Check the A/C system for leaks. Is the system free from leaks? | Go to Step 13 |
DIAGNOSTIC PROCEDURE
V5 A/C System (Automatic Control Type) Description
Refer to V5 A/C System (Manual Control Type) Description for general information details for the following
- System Components - Functional.
- The V5 A/C System.
- V5 Compressor - Description of Operation.
- V5 Compressor - General Description.