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Converting Porsche 924 to R 134

Showing 4 out of 4 Posts
Question From neutron on Converting Porsche 924 to R 134

1982 Porsche 924 Turbo (hobby car)
Converting from R 12 to R 134
70 K miles (but compressor is probably not original since correct part number V belt does not fit) Label on compressor says York Automotive, Mfd by Diesel Kiki Co., LTD Japan Part # 488-22023. It doesn’t look like some of the pictures in my factory manuals but it’s my understanding that the AC units on these cars are Japanese. My manuals for the 924 says the charge is 30 oz of R 12 and 7.8 oz. (says 6 oz. in another place in the book) Suniso # 5 GS oil “in new Compressor” or 4.4 oz after oil is distributed through the system.
AC was last worked on & charged Sept 2006 and 49k miles and has worked fine until this summer. I was advised at that time not to convert to R134 because “this system didn’t convert well” and R12 was still available. It cools in the mornings but can’t keep up in 95 degree afternoon and I see bubbles in the sight glass on the receiver-drier. I have checked most of the hose connections I can see and the condenser I can see for oily residue and find none. Haven’t been under the dash to the evaporator yet but I find nothing oily from the condensation drain pipe under the car. I don’t think hose connections have those green O rings as they seem to be AN type fittings. 8 fittings I think.
I haven’t found a shop yet that has R12 so I’m thinking I may have the R12 recovered then convert the system myself. While I am not formally trained, I have an understanding of how the system works, manuals, and video training material. (I’m an electronics technician) I have cheep R134 gages, an AC Flush Gun and can rent a vacuum pump. I would access the evaporator from under the dash per the directions in my manual and disconnect the hoses, disconnect hoses at the condenser, receiver-drier, and compressor to flush the system components (except compressor) and hoses. Reassemble with new receiver-drier and pull a vacuum to test.
I have these question please:
1. Am I correct that a leak will be indicated by an oily residue?
2. Is there a reason why this particular car should not be converted to R134 other than the compressor is hard to get to and the high and low (or S & D as they are labled) fittings are both on the back of it?
3. The compressor seems to have a reservoir for oil and the exploded view in my manual shows an oil filler plug. (the compressor is round and seems to have 5 cylinders however again I don’t know that I have an original compressor but there is a filler plug) Is just turning the compressor over and letting the oil drain out be sufficient or do I want to put solvent in there?
4. Will the evaporator flush through the expansion valve or do I need to dissemble that too?
5. The clutch on the compressor seems to have a slight bit or oil on it. Does that sound normal or should it be dry and dusty? It runs and doesn’t make any noise.
6. What else have I not considered? I think I read somewhere that the pressure switch would need to be changed to some other value or something.
7. I have a 134 kit from a few years ago that has 3 cans of 10 oz.134 / 2oz. of oil plus other stuff. I figure the R 134 charge would be 25.5 oz. Should of get plane R134 and a separate can of Ester oil? Put all of the ester oil in the compressor or put some in other parts of the system? Guess I will add leak dye as well
Thanks for any help

Response From Discretesignals

These are the minimum requirements for conversion on your vehicle:


NOTE: When available, Original Equipment Manufacturer (OEM) procedures on R-134a retrofitting are found in Technical Service Bulletins (TSB). Always check for TSBs prior to retrofitting, some vehicles can not be retrofitted.

- All traces of the original refrigerant must be removed. Under the provisions of the EPA's Significant New Alternative Policy (SNAP), mixing differing types of refrigerant is prohibited. Separate, dedicated, EPA approved equipment must be used to recover and store the R-12 removed from the system.

NOTE: It is illegal to vent any type of refrigerant to the atmosphere.

- The system should be inspected thoroughly for leaks and deteriorated components. If the system is operational it should also be checked for proper performance. Any deficiencies noted should be corrected prior to retrofitting.

NOTE: Due to the less efficient cooling characteristics of R-134a, a properly charged R-12 system which is performing poorly prior to retrofitting will not produce satisfactory cooling performance after retrofitting.

- Unique R-134a Fittings must be added to all service ports, or the service port must be permanent disabled.

- The original refrigerant service label should be removed and a new R-134a service label should be installed.

- All exising mineral oil should be removed from the system and replaced with either:
- Polyalkaline Glycol (PAG) oil
- Polyol Ester (POE) oil **don't recommend using Ester.** Use Nd-8 oil.

CAUTION: Always review TSBs for manufacturer specific oil requirements. Some manufacturers require a specific type (PAG or POE).

- If any components are removed, R-134a compatible gaskets and O-rings should be used during installation.

- If A/C hoses are replaced, barrier type hose should be installed.

NOTE: Non-barrier type neoprene hoses may be identified by the thin ribbing running the length of the hose. Non-barrier hoses are often thicker and more flexible than barrier hoses.

- The amount of R-134a charged into the system should normally be 80-90 % of the amount of R-12 required in a fully charged system. Check Technical Service Bulletins (TSB) for specific amounts.

NOTE: Experience has shown that a fully charged R-134a retrofitted system may still exhibit bubbles flowing through the sight glass.

These are optional modifications:

To compensate for the higher vapor temperature of R-134a, the following may be needed to increase heat removal capacity and provide satisfactory cooling performance. Insufficient heat removal capacity may be indicated by high system pressures and warm outlet temperatures.

Improved Condenser
Older model tube and fin condensers should be replaced with more efficient Serpentine or Parallel flow style condensers. Smaller, reduced area condensers may need to be replaced with larger condensers to provide sufficient heat removal capacity.

NOTE: Cleaning the debris from in front of and behind the condenser can dramatically improve the systems cooling performance.

Improved Air Flow
Electric Pusher Fans - An auxiliary fan may be needed to provide additional airflow over the condenser.

More Efficient Fan Blades - Older vehicles may be equipped with 2 bladed fans. Replacing this type of fan with newer, more efficient multi-bladed fans will increase the airflow across the condenser, resulting in improved cooling performance.

Fan Clutch Operation - On belt driven fans, verify the fan clutch is operating properly. If there is any evidence of leakage from the clutch, it should be replaced. Replacing the clutch with a heavy duty model may be necessary to provide adequate airflow.

NOTE: Prior to installing new fans or fan clutches, verify that all fan shrouds and air dams are present and undamaged.

Replace Non-Barrier Hoses - Because R-134a is made up of molecules which are much smaller than those in R-12, older non-barrier type hoses may leak when used with R-134a.

Early testing indicated that non-barrier type hoses would need to be replace during all R-134a retrofits. Recent testing has shown that the mineral oil used in lubricating the R-12 systems saturates the inner walls creating a sufficient barrier to prevent R-134 leakage.

NOTE: If the system is flushed, the oil saturation barrier will be removed and the non-barrier hoses will need to be replaced to prevent leakage.

Replace O-Rings and Seals - Any fitting which has been disturbed during the retrofit procedure should have the O-ring or seal replaced with one which is R-134a compatible. To prevent leakage, new O-rings and seals should be coated with mineral oil prior to installing.

Compressor Replacement - The higher system pressures associated with R-134a could result in premature failures of worn compressors. Seals within the compressor may not be compatible with R-134a, resulting in seal failure and leakage.

NOTE: Always consult Technical Service Bulletins (TSB) prior to performing an R-134a retrofit. Some compressors are not compatible with R-134a and must be replaced.

Replace Receiver/Dryer/Desicant - Replacing the desicant helps assure a dry, moisture free cooling system. Replacing the Receiver/Dryer allows for removing any non-compatible mineral oil which may have collected in it.

Flush Condenser - If there has been a compressor failure or the compressor is worn flushing the condenser will remove any debris which might block refrigerant flow or cause further damage to the compressor.

NOTE: If any non-barrier hoses are flushed they will need to be replaced with barrier hoses to prevent refrigerant leakage.

If a vehicle is not equipped with a high pressure compressor shut-off switch, it is highly recommended to install one. Due to the higher operating pressures of R-134a it is very important to disengage the compressor prior to a component failure resulting from excessive pressure.

Response From Discretesignals



Binder - Service Technical Bulletins

Climate Control System Refrigerant 134a Use

Vehicle Type: All

Model Year: Up to 1992

Use of refrigerant substitutes. (sometimes referred to as "drop-in's")

In the interest of protecting the ozone layer, the manufacturing of refrigerant type R12 has not been permitted since January 1, 1996. As a replacement for refrigerant R12, most manufacturers, including Porsche, have required the use of refrigerant type R134a. This applies to new vehicles (as of 1993), as well as existing vehicles originally equipped with type R12 climate control systems.

In spite of the R12 restrictions, there are products being developed and sold in the after market as R12 substitutes, or "drop-in's". These products have NOT been tested for compatibility with Porsche vehicles, and therefore ARE NOT APPROVED by Porsche. The only approved replacement for refrigerant type R12 on Porsche vehicles is refrigerant type R134a.

Please refer to Technical Bulletin Group 8, number 9501 when retrofitting a Porsche climate control system from refrigerant R12 to refrigerant R134a. Special situations apply to those models not referred to in this Technical Bulletin. Contact Technical Services before attempting a refrigerant R134a retrofit on any model not covered in this Technical Bulletin.

"Drop-in" refrigerant R12 substitutes are not approved for use in Porsche vehicles. Any damage or failure resulting from the use of these "drop-in's" will not be considered a warranty matter.

Response From Discretesignals Top Rated Answer

Technical Bulletin Group 8 number 9501. .pdf file