Troubleshooting Troubleshooting – Heating, Ventilation, and Air Conditioning (HVAC) Estimated reading: 3 minutes Contributors Overview This troubleshooting guide assists Porsche 944 S / S2 (16v ,1989–1991) owners in diagnosing and resolving common issues with the heating, ventilation, and air conditioning (HVAC) system. Proper HVAC function is critical for driver comfort and vehicle performance, particularly in the S / S2 variant, which uses late-model alloy control arms and advanced climate control systems. The following procedures address water leakage from dash vents, persistent hot air output, alternating hot/cold air, and issues with the A/C pushbutton (“snowflake” switch). Pink and blue text represents links to additional resources, tools, parts, and partner websites. Water Comes Out of Dash Vents Possible Cause: Clogged HVAC condensate collection pan drain line. Checks: Behind the center console, locate the drain line (approximately 1/2″ in diameter) connected to the bottom of the HVAC unit, routed into the top of the torque tube tunnel. Procedure: Gather plenty of rags, as a clogged line may cause condensation to spill from the HVAC unit’s condensate collection pan. Remove the drain line and clean it thoroughly. Insert a finger into the drain at the bottom of the collection pan to check for and clear any blockages. Reconnect the line, ensuring it is properly routed onto the top of the torque tube tunnel. Ventilation System Blows Hot Air All the Time Possible Cause: Multiple issues may cause the ventilation system to blow hot air continuously in the 16v S / S2. Checks: Refer to the detailed troubleshooting procedure in the Porsche 944 Workshop Manual or specialized HVAC diagnostics (HVAC-01). Procedure: Follow the HVAC-01 procedure in the Porsche 944 Workshop Manual for the 16v S / S2 to diagnose and address this issue. Ventilation System Alternates Between Hot and Cold Air Possible Cause: Dirty interior air temperature sensor. Checks: A small fan supplies airflow to the interior air temperature sensor, located behind the small round vent next to the cigarette lighter. Trace the tube toward the firewall to find the sensor (refer to HVAC-01 for images). Procedure: Follow the HVAC-01 procedure in the Porsche 944 Workshop Manual to clean or replace the interior air temperature sensor. A/C Pushbutton (“Snowflake” Switch) Will Not Stay Engaged Possible Cause Checks Procedure Button latch has failed. Inspect the temperature control unit for a faulty pushbutton latch. Remove the temperature control unit and replace the pushbutton. The pushbutton is available from suppliers like Pelican Parts, despite some dealers claiming it is discontinued or requiring full unit replacement. Sources Clark’s Garage Pelican Parts Porsche 944 Workshop Manuals YouTube Tagged:Air ConditioningHVACVentilation Troubleshooting – Heating, Ventilation, and Air Conditioning (HVAC) - PreviousTroubleshooting – Fuel SystemNext - Troubleshooting – Heating, Ventilation, and Air Conditioning (HVAC)Troubleshooting – Manual Transmission
