Air Conditioning Troubleshooting and Repair – 2.5L NA

Overview

This procedure provides troubleshooting steps and repairs for the Porsche 944 8-valve engine variants Air Conditioning system, covering both the pre-1985.5 and 1985.5 onwards models. Proper troubleshooting ensures the system functions effectively, maintaining comfort and reliability.

Pink and blue text represent links to additional resources, tools, parts, and partner websites.

Tools Required

• A/C Gauges and hose set
• Basic mechanic’s hand tools

Step-by-Step Procedure

Step 1: Understanding Your 944 A/C System

1. The Porsche 944 uses an expansion valve type air conditioning system.
2. The main components are the compressor, condenser, receiver-drier, expansion valve, and evaporator.
3. The receiver-drier is located behind the driver’s side headlight (LHD vehicles).
4. The expansion valve is located near the passenger footwell (LHD vehicles), next to the firewall.

Step 2: Basic A/C System Troubleshooting

5. Attach your A/C gauges to monitor high and low-side pressures.
6. Compare your readings to standard pressure charts listed below under various ambient temperatures.

Step 3: Diagnose Specific Issues

Low Compressor Discharge Pressure:

Check for leaks, replace expansion valve, or recharge refrigerant as necessary.

High Compressor Discharge Pressure:

Ensure condenser is clean, verify the fan belt tension, and check refrigerant charge levels.

Low Suction Pressure:

Inspect for kinked hoses, moisture contamination, or refrigerant shortage.

High Suction Pressure:

Inspect expansion valve for proper operation, verify refrigerant charge level.

Compressor Not Working:

Check compressor belt and clutch wiring, verify refrigerant charge, replace thermostat if faulty.

Evaporator Not Cooling:

Adjust thermostat settings, inspect for air leaks, replace receiver-drier or expansion valve if blocked.

Frozen Evaporator Coil:

Replace faulty thermostat, check duct hoses for proper airflow.

Step 4: A/C System Pressure Reference Chart

8. Verify your pressure readings against the following reference values based on ambient temperature:
   • 60°F (16°C): Low Side 28-38 psi, High Side 130-190 psi
   • 70°F (21°C): Low Side 30-40 psi, High Side 190-220 psi
   • 80°F (27°C): Low Side 30-40 psi, High Side 190-220 psi
   • 90°F (32°C): Low Side 35-40 psi, High Side 190-225 psi
   • 100°F (38°C): Low Side 40-50 psi, High Side 200-250 psi
   • 110°F (43°C): Low Side 50-60 psi, High Side 250-300 psi
   • 120°F (49°C): Low Side 55-65 psi, High Side 320-350 psi

Post Procedure Checklist

• Ensure all fittings and connections are tight with no leaks.
• Recheck A/C system pressure and functionality.
• Verify proper vent temperature according to ambient conditions.

Sources

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