How to Perform an A/C Retrofit (Procedure Manual )
How to Perform an A/C Retrofit - Generic Instructions Except QuestThis procedure is used to replace R-12 refrigerant with R-134a refrigerant for Nissan vehicle A/C systems. For specific component removal and installation procedures, refer to the appropriate vehicle service manual.
Required Equipment
^ A set of R-12 service equipment certified to meet the requirements of SAE J1991. The J38750-A, ACR3 Recovery / Recycling / Recharging station meets these specifications.
^ A set of R-134a service equipment certified to meet the requirements of SAE J2210. The J39500-A, ACR4 Recovery / Recycling / Recharging System meets these specifications.
^ An adequate supply of R-134a refrigerant.
^ An adequate supply of PAG type "S", "R", and "F" A/C lubricant. Use only the lubricant specified for a particular system. Refer to the application table shown on page 3 of this bulletin.
Preliminary Checks
1. Before servicing any A/C system, determine which type of refrigerant and lubrication oil is currently in the system. This is important in order to avoid contamination of your existing refrigerant supplies or potential damage to your refrigerant equipment.
2. Ask the customer about the A/C service history. Have any alternative refrigerants been installed in the system? Has an A/C retrofit already been performed?
3. Check the engine compartment for A/C labels which may indicate previous retrofit work, oil additives, etc..
4. Verify the system you are working on, R-12 or R-134a.
Caution:
^ Always wear eye and hand protection (goggles and gloves) when working with any refrigerant or A/C system.
^ Avoid breathing A/C refrigerant and lubricant vapors or mist. Exposure may irritate eyes, nose, and throat. To remove R-134a from the A/C system, always use service equipment certified to meet the requirements of SAE J2210 (R-134a recycling equipment). Additional health and safety information may be obtained from refrigerant and lubricant manufacturers.
^ Do not release refrigerant into the atmosphere. Use approved recovery / recycling equipment to capture the refrigerant every time an air conditioning system is discharged. If accidental discharge occurs, ventilate work area before resuming service.
^ R-134a service equipment or vehicle A/C systems should not be pressure tested or leak tested with compressed air. Some mixtures of air / R-134a have been shown to be combustible at elevated pressures. These mixtures are potentially dangerous and may result in fire or explosion causing injury or property damage. Additional health and safety information may be obtained from refrigerant and lubricant manufacturers.
When installing refrigerant components, observe the following:
^ Do not remove the seal caps until just before connecting components (refer to "A" in Figure 1).
^ Be sure the O-ring is on the tube end and apply a small amount of refrigerant lubricant to the O-ring before assembling (refer to "B" in Figure 1).
^ Install tubes into mating parts and finger tighten nuts.
^ When tightening fittings, be sure to use a torque wrench and back up wrench (refer to "C" in Figure 1).
Retrofit Preparation
5. Determine the parts required for the vehicle system being retrofitted.
6. Conduct a "pre-retrofit performance test":
^ If the system is functioning properly, proceed to step 7
^ If the system is not functioning properly, determine the cause
^ If the system does not contain the proper amount of refrigerant, charge the system to 50 PSI with R-12 refrigerant and identify any leaks and/or failed components
^ If the system is still not functioning, proceed to step 7.
7. Recover the refrigerant using approved R-12 recovery / recycling equipment.
8. Repair or replace any failed components with the appropriate replacement.
NOTE:
When replacing a failed compressor, prior to retrofit, determine the type of lubricant the replacement contains. If the replacement compressor contains a lubricant other than the specified PAG lubricant, drain that lubricant before installation.
9. Disconnect the negative battery cable.
Passenger Compartment
10. Remove the evaporator assembly as follows:
A. Disconnect the high and low pressure tubes from the evaporator assembly.
B. Disconnect the harness connector from the blower motor resistor (as necessary).
C. Remove and save all mounting hardware.
D. Remove the evaporator assembly.
Thermal Expansion Valve (TXV) Installation
11. Remove and save the resistor bucket (2 screws) from the evaporator case assembly (if equipped).
12. Remove the thermistor from the evaporator core (if equipped). Note the thermistor location so it can be re-installed to its original location.
13. Remove and save the case halves from the evaporator core. (Carefully cut the air seals where the case halves meet).
14. Remove and discard the TXV bulb insulating wraps.
15. Disconnect the TXV equalizer tube from the evaporator outlet tube (use a backup wrench).
16. Remove the TXV sensing bulb from the evaporator outlet tube (1 clip).
17. Remove and discard the TXV (2 fittings).
18. Remove and discard O-rings on the TXV inlet and outlet tubes. Clean the tube ends.
19. Using new O-rings, install the new TXV onto the evaporator core.
20. Connect the TXV equalizer tube to evaporator outlet tube (lubricate the O-ring with the appropriate PAG lubricant as required) and torque fittings to specification (use a backup wrench).
21. Secure the TXV sensing bulb to the evaporator core.
22. Install new insulator foam wrap around the TXV sensing bulb.
23. Install new insulator butyl tape around the TXV.
24. Reassemble the case halves to the evaporator core.
25. Reinstall the thermistor to its original position (if equipped).
26. Reinstall the resistor bucket to the evaporator case (if equipped).
27. Repair air seals. If seals are not suitable for reuse, replace with new ones (available separately through NMC parts supply).
28. Reinstall the complete evaporator assembly into the vehicle in the reverse order of removal. Install new O-rings on the evaporator inlet and outlet tubes.Lubricate the O-rings with the appropriate PAG lubricant.
29. Reconnect the low and high pressure tubes to the evaporator. Torque fittings to specification.
30. Affix the "Retrofitted to R-134a" label to the evaporator case in a visible location. (Refer to Figure 2).
31. Remove and discard the existing pressure relief valve from the high pressure side (compressor side) flange.
32. Install the new pressure relief valve onto the high pressure hose flange. Lubricate O-ring with the appropriate PAG lubricant.
Torque the pressure relief valve to specification.
33. Affix the "Retrofitted to R-134a" label to the compressor in a visible location as shown in Figure 3.
Liquid Tank Removal / Installation
34. Disconnect the liquid tank (LT) switch harness from the vehicle harness.
35. Remove and save the pressure switch from the old LT.
36. Disconnect the tubes from the LT. Remove the LT.
37. Remove and discard the blind plug from the new LT. Make sure the fusible plug remains in the new LT.
38. Install the old pressure switch into the new LT blind plug port, use a new O-ring. Lubricate with appropriate PAG lubricant.
39. Loosely install the new LT into the LT bracket.
40. Reconnect the pressure switch harness connector to the vehicle harness.
41. Install new O-rings on the LT inlet and outlet tubes. Lubricate O-rings with the appropriate PAG lubricant.
42. Reconnect the tubes to the LT. Torque to specification.
43. Tighten the LT bracket pinch bolt to secure the LT in the LT bracket.
Final Assembly
44. Install the charge adapters to the high and low pressure service valves. Torque adapters to specification (use a backup wrench).
NOTE:
THERE ARE TWO TYPES OF HIGH PRESSURE SERVICE VALVES 7/16-20 UNF AND 3/8-24 UNF. BOTH SIZES OF ADAPTERS ARE INCLUDED IN THE RETROFIT KIT. INSTALL THE CORRECT ADAPTER AFTER CONFIRMING THE SERVICE VALVE CONFIGURATION.
45. Using an ink pen, completely fill out the retrofit label. After filling out the label, peel the backing from the label's adhesive clear cover shield and firmly press the cover shield against the label face to permanently seal the label.
46. Affix the caution label to the engine room wall or suitable (permanent under-hood body panel) visible location as shown in Figure 6. Make sure the surface is clean before installing the label.
47. With a permanent marker, delete references to R-12 from the original caution label.
48. Reconnect the negative battery cable.
After Installation
49. Evacuate the A/C system for a minimum of 30 minutes.
50. Add the appropriate PAG oil as specified in the "Lubricant / Refrigerant Specification Chart" shown in this bulletin.
NOTE:
Do not compensate for lubricant change. Add the full amount indicated in the "Lubricant / Refrigerant Specification chart.
51. Charge the A/C system with the specified amount of R-134a refrigerant. (Refer to the "Retrofit Lubricant / Refrigerant Specification" chart in this bulletin).
52. Perform a refrigerant leak test using Kent-Moore tool J39400 to insure there are no refrigerant leaks.
53. Conduct an A/C performance test. (Refer to the "Performance Characteristics" information listed below).
Performance Characteristics for Retrofitted A/C Systems
General performance characteristics for R-12 A/C systems and the retrofit R-134a systems differ. These differences are outlined below:
Recirculating-to-discharge Air Temperature
^ The retrofitted system retains the original R-12 heat exchanger (evaporator and condenser)
^ Some R-12 lubricant oil remains in the A/C system
^ Because of these two reasons, the retrofit A/C system has a slightly lower cooling capacity than the R-12 A/C system. The maximum discharge temperature is increased by approximately 3.6 deg. F (2 deg. C).
Ambient Air Temperature-to-Operating Pressure
The retrofit A/C system has a higher operating pressure than the R-12 A/C system when the outside temperature exceeds 59 deg. F (15 deg. C).
^ High pressure side (discharge side): Maximum pressure increase of approximately 43 PSI (294 kPa, 3 kg/cm.).
^ Low pressure side (suction side): Same as R-12 A/C system.
Refer to the appropriate service manual for discharge air temperatures and operating pressure values for individual models. After verifying the discharge air temperature is within specifications, the retrofit is complete.