General Retrofit Procedures (3-22-1999)

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When to Retrofit?: Vehicles with A/C systems designed for R12 should be serviced with R12 as long as the supply lasts or until the price would make a retrofit practical. As of the MACS convention of 1999 this is still the stand of all the OEMS! All the OEM's also recommend that you use only R134a when you do retrofit. The A/C industry recognizes the need to retrofit A/C systems in the near future and is working out the details.

SPECIAL NOTES:

These retrofits procedures are a combination of OEM and after market recommendations.

All retrofit procedures must follow SAE guidelines.

See specific guide lines provided by TSB's (Technical Service Bulletins) of the manufacturer of the vehicle or in a retrofit manual such as Four Seasons Pn 59148.
My recommendations are in line with the aftermarket recommendations. Aftermarket recommendations are those of companies such as Everco, Four Seasons and Murray.
The customer needs to have the refrigerant options and short commings of R-134a explained to them befor you retrofit. Once the vehicle has been retrofitted, it would cost a lot to convert it back should they change their minds.
MAKE SURE YOU NOTICE:
The OEM's recommend that you don't flush and that you use PAG oil. The OEM's note that PAG oil will not mix with mineral oil. They say that most of it will park and not effect the retrofit.

The aftermarket companies like Four Seasons recommend that you flush and that you use Ester oil.
So if you don't flush consider using PAG oil. If you don't flush and use Ester oil, it will mix with mineral oil that is left in the system. Will this mixture park and not lubricate the compressor?

MINERAL OIL REMOVAL & FLUSHING

Ever one agrees that too much oil will decrease performance. The more mineral oil that is removed the better. Flushing also remove debris and contaminants.
See Flushing Procedures

OEM RECOMMENDATIONS:: Most all OEM (original equipment manufactures) do not recommend that you flush and they all recommend you use PAG oil. GM states that the normal charge of mineral oil left in the A/C system after retrofit with R134a will not harm system operation. GM's tests indicate that mineral oil does not mix with R134a, and will park in places such as the accumulator and evaporator. GM further states that mineral oil and PAG oil are chemically compatible. GM recommends the use of in-line filters as an alternative to flushing. GM states that any residual flushing solvent left in an A/C system may be very damaging and that it may also be incompatible with R134a.
AFTER MARKET RECOMMENDATIONS:: The opinion of the after market part suppliers is to flush the A/C system to remove oil and contaminants and they recommend that you use Ester oil. They recommend you flush with HFCF-141b.
MY RECOMMENDATIONS:: You should remove as much oil as practical and note what you did for further reference. Systems that have signs of debris and contaminants from compressor failure or desiccant breakdown should be flushed. You should flush the condenser, evaporator and hoses where practical. Systems that can be flushed in under a hour should always be flushed. Systems that have the evaporator and expansion valve under the dash where there flushing would be impractical could still have other measures taken to remove mineral oil. You could remove and drain the compressor if it's practical. The replacement of the filter drier/accumulator removes another few ounces of mineral oil. You could flush the components under the hood as the discharge hose, the condenser and the liquid line. You should never flush the compressor, receiver drier/accumulator, expansion valve, orifice tube, orifice tube line or any other refrigerant control valves! I replace the orifice tube line when ever I change a compressor.
See Flushing Procedures

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O-RINGS & GASKETS: All o-rings and gaskets replaced should be R134a compatible. Coat all o-rings, seals and fittings with mineral oil. Top Of Page

HOSE REPLACEMENT: The after market and the OEM manufactures recommend that you don't need to change the hoses unless they show signs of leaks. If you replace the hoses, it should be with Barrier style hose and Beadlock fittings.
More Hose Information Top Of Page

COMPRESSOR: Most OEM manufactures state that the compressor is not part of the normal retrofit. When you do change a compressor make sure you know what type oil it contains. Four Seasons has been manufacturing their compressors to be compatible with R-134a for the last three years. Four Seasons now ships their compressors dry. We always check! Top Of Page

CONDENSER AND AIR FLOW (HEAT EXCHANGE)

One of the major problems with retrofits to R134a is high head pressure caused by poor heat exchange at the condenser. Any heat exchange and air flow improvement you can make will only help the operation of the A/C system!
Things that should be considered:

Make sure it has clean fins and good air flow.
Add seals around the condenser to improve the air flow through it.
Increase the air flow by changing the fan clutch or the coolant fan motor.
Make sure that any air dams etc. are not missing.

The need to change the condenser will be on a vehicle by vehicle bases. The need will depend on the climate, conditions of use, the size of the vehicle, and the other components as evaporator(s). If it is necessary to replace the condenser, try to use a newer improved version (multiflow model). The head pressure of the air conditioning system will tell you if the old condenser is sufficient. Any head pressure over 250 PSI will hamper cooling and any head pressure over 325 PSI should be considered overheating. Air conditioning manufactures have made design changes to condensers for use with R134a.
More Condenser Information Top Of Page

FILTER DRIER / ACCUMULATOR REPLACEMENT: The after market recommends that you change the filter drier/accumulator with one that contains XH-7 or XH-9 desiccant. The OEM manufactures are split on this subject but recognize that a new drier/accumulator with compatible desiccant will improve the retrofit. Ford & GM state that changing the drier/accumulator is not mandatory or covered under warranty. This policy may be to keep them from spending money when the retrofit is done under warranty. When replacement is done, Ford & GM recommend using driers/accumulators with XH-7 or XH-9 desiccant. Top Of Page

EXPANSION VALVE: The OEM manufactures state that the expansion valve is not part of the normal retrofit. R12 expansion valves and orifice tubes should provide adequate service when retrofitting. Some shops I have talked to install new expansion valves when they retrofit a dual evaporator systems. Top Of Page

EVAPORATOR: The OEM manufactures state that the evaporator is not part of the normal retrofit. R12 evaporators should provide adequate service when retrofitting. Systems that performed well with R12 should perform fine with R134a. Top Of Page

Suction Control Valves for Non-Cycling Compressors: Recommendations From A/C Shops and Aftermarket:
Suction Throttling Valves (STV) control and cycle the minimum pressure in the evaporator, there by controlling and cycling the minimum temperature of the evaporator. They should be adjusted back 3 to 4 PSI with R-134a in order to achieve the same temperature. This is because the pressure temperature relationship of R-12 and R-134a is different. For instance at 25 °F the pressure of R-12 is 24.6 PSI and the pressure of R-134a is 22.1 PSI.
Pressure Temperature Table
Most valves will have a lock nut and an adjustment screw on the inlet end. One eight turn counterclockwise lowers the low side pressure approximately 2 PSI and one quarter lowers the low side pressure approximately 4 PSI. Top Of Page

CLUTCH CYCLING SWITCH: Recommendations From A/C Shops and Aftermarket:
Lower the adjustment of the clutch cycling switch to 21 to 22 PSI with R-134a. This is because the pressure temperature relationship of R-12 and R-134a is different. For instance at 25 °F the pressure of R-12 is 24.6 PSI and the pressure of R-134a is 22.1 PSI.
Pressure Temperature Table
If it is adjustable there will be an adjustment screw between the two terminals. One eight turn counterclockwise lowers the cut out pressure approximately 2 PSI and one quarter lowers the cut out pressure approximately 4 PSI. Top Of Page

HIGH PRESSURE RELIEF VALVE (HPRV): Some OEM manufactures recommend the replacement or HPRV when you perform a retrofit. The common HPRV used by GM, York, and Tecumseh vents at approximently 430 PSI. Its part number (Pn) is as follows: Delco Pn "DE 15-5415" Everco Pn "EV A7247" Four Seasons Pn "4S 35753" Murray Pn "MUR 209583" The high pressure relief valve should have a setting at least 50 PSI above the HPCO. If you install a HPCO switch it will keep the HPRV from venting in the first place, which is a much better approach. Top Of Page

HIGH PRESSURE CUTOUT (HPCO) SWITCH: I think a high pressure cut out switch is a worth while safeguard. A HPCO switch could save a retrofit from being a monster! I have heard of retrofits of dual evaporator systems that ran such high head pressures that the hoses swelled and started leaking. Red Dot manufactures a switch called a Trinary switch that is reasonable in price (about $20.00), performs functions needed in a retrofit and R134a compatible.
Four Seasons part numbers are: 35899 (male style), 35901 (Female 1/4" service port style), or 35922 (universal male or female style).
It performs three functions:
1- It's a high side low pressure (HSLP) switch which opens at about 23 PSI. It would keep the compressor from coming on if the refrigerant is lost or ambient temperature is low.
2- It's a HPCO switch witch opens at about 325 PSI. It would stop the compressor from operating if the head pressure goes above 325 PSI.
3- It's a cooling fan switch witch closes at about 220 PSI. It could be used to control a cooling fan. Its part number is: RD 71R7550, 4S 35922, EV A8025, MUR 207094, TA 11-2629. Top Of Page

OIL REPLACEMENT: The OEM manufactures recommend that you not flush and fill the system with a full charge of the proper PAG oil. The after market manufactures recommend that you flush and refill the system with a full charge of the proper Ester oil. The general recommendation is to use PAG oil if you don't flush and use Ester oil if you do flush. These are the two avenues that are being recommended and tested.
You could also use Ester oil with R12 now and then change over the system to R134a later. If this was done with a flush and a R12/R134a drier, there would be very little to do later. Ever one emphasizes the fact that the new oils will absorb moisture from the air readily and that the container must be keep sealed at all times. I add fluorescent dye to all systems that have a leakage history. There are different dyes for different types of lubricant.
Refrigerant Oil Information
PAG & ESTER Compressor Oil Recommendations Top Of Page

SERVICE PORT ADAPTERS: Special R134a only service ports that meet SAE requirements are required by law. R12 service ports not in use should have block of caps put on them. The ports should have a thread lock on them to prevent removal. The 90 degree service ports must have the valve core removed. Top Of Page

REFRIGERANT REPLACEMENT FOR R12

R134a as the only substitute for R12 refrigerant that is recommended by the OEM and after market manufactures. The general recommendation is to recharge the system with about 15% to 20% less R134a than the R12 specification. General Motors' formula is: (R12 lbs x .9) - .25 lb. = R134a Charge The sight glass is not a good indicator of charge!

Notes on blends:

By law each refrigerant must use unique service fittings.
By law each refrigerant must use unique labels.
You must maintain charging and recover equipment for that refrigerant.
Refrigerant blends may leak out a part of their mixture and become a unusable hazardous waste.

Refrigerant Information
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LABEL: Special R134a service labels that meet SAE requirements are required by law. Top Of Page

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PParish
70 North West St.
Dover, DE 19904
DATE: Jan. 21, 1997
E-mail address: PParish@delanet.com/