Refrigerant Evacuation and Recharge

Overview

This procedure outlines how to evacuate and recharge the air conditioning (A/C) system on a Porsche 944 S / S2 with a 16v engine. The process removes old refrigerant, checks for system integrity, and recharges with R134a refrigerant to restore cooling performance. A properly charged A/C system ensures comfort in hot weather and prevents compressor damage due to low refrigerant. This guide assumes the system uses R134a, as most S / S2 models have been converted from R12. If R12 is present, professional servicing is required.

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Tools Required

• Manifold gauge set (compatible with R134a)
• Vacuum pump (minimum 5 CFM)
• R134a refrigerant canister with gauge
• Leak detection kit (UV dye or electronic sniffer)
• 10mm (3/8 inch) wrench
• 13mm (1/2 inch) wrench
• Safety glasses and gloves (nitrile and leather)
• Torque wrench (covering 10-20 Nm / 7-15 ft-lbs)
• UV flashlight (if using dye for leak detection)

Parts Required

• R134a refrigerant (approximately 680g / 24 oz for S / S2)
• PAG-46 oil (100-150 mL, 000 043 305 15)

Step-by-Step Procedure

Step 1: Prepare the Vehicle and Safety Precautions

1. Park the vehicle on a flat surface in a well-ventilated area, away from open flames or sparks.
2. Ensure the engine is off and the A/C system is not running.
3. Wear safety glasses and gloves (nitrile under leather) to protect against refrigerant burns.
4. Check the engine bay sticker near the radiator to confirm the A/C system uses R134a. If R12 is indicated, stop and seek professional servicing.

Step 2: Locate and Access A/C Ports

5. Locate the low-pressure port on the compressor (driver’s side wheel well, turn steering wheel left for access) and the high-pressure port near the receiver/drier (near the radiator).
6. Remove the caps from both ports using a 10mm (3/8 inch) wrench if needed, and inspect Schrader valves for damage.
7. Briefly depress the high-pressure port’s Schrader valve (with gloves and glasses) to check for residual pressure. If gas escapes, proceed cautiously.

Step 3: Evacuate the A/C System

8. Connect the manifold gauge set: blue hose to low-pressure port, red hose to high-pressure port, yellow hose to vacuum pump.
9. Open both high and low-side valves on the manifold gauge set.
10. Run the vacuum pump for 5 minutes to check for major leaks. The gauge should hold at -0.8 to -1.0 bar (-24 to -30 inHg).
11. If the vacuum holds, continue pulling for 30 minutes to remove moisture and residual refrigerant.
12. Close the manifold valves, turn off the pump, and monitor the gauge for 10 minutes. A pressure rise indicates a leak; use a UV dye kit or sniffer to locate and repair it.

Step 4: Add PAG Oil

13. Disconnect the vacuum pump and attach the yellow hose to a PAG-46 oil injector (000 043 305 15).
14. Add 100-150 mL of PAG-46 oil via the low-pressure port, per the Porsche 944 Workshop Manual specifications.

Step 5: Recharge the A/C System

15. Connect an R134a canister (approximately 680g / 24 oz) to the yellow hose of the manifold gauge set.
16. Purge the yellow hose by briefly opening the valve until refrigerant escapes, then tighten.
17. Start the engine and set the A/C to maximum cooling with the fan on high.
18. Open the low-side valve to allow refrigerant to enter. Keep the high-side valve closed.
19. Monitor the low-side pressure (1.5-2.5 bar / 22-36 psi) and the sight glass near the receiver/drier (minimal bubbles when fully charged).
20. Close the low-side valve when the system is charged (approximately 680g / 24 oz).
21. Turn off the engine, disconnect the gauge set, and replace port caps, tightening to 10 Nm (7 ft-lbs).

Step 6: Test the System

22. Start the engine and run the A/C on maximum cooling for 5 minutes.
23. Measure vent temperatures with a thermometer (should be 4-10°C / 39-50°F at 25°C / 77°F ambient).
24. Check all connections for leaks using a UV flashlight (if dye added) or electronic sniffer.
25. Drive the vehicle for 5 miles (8 km) to confirm consistent cooling under load.

Post Procedure Checklist

• Verify vent temperatures are 4-10°C (39-50°F) at idle and during driving.
• Check for leaks at all A/C connections using UV dye or an electronic sniffer.
• Ensure the compressor engages without unusual noises.
• Confirm the sight glass shows minimal or no bubbles when the A/C is running.
• Check that port caps are tightened to 10 Nm (7 ft-lbs).

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube