Troubleshooting - Heating, Ventilation, and Air Conditioning (HVAC)
Symptom-driven guide to diagnosing HVAC problems on the Porsche 944, including water from vents, constant hot air, alternating hot and cold air, and a stuck A/C pushbutton.
Difficulty: Moderate2 min readApplies to: 944 · 944S · 944S2 · 944 Turbo
Introduction
This troubleshooting guide is intended to help identify and repair heating and air conditioning problems. Symptoms covered:
- Water comes out of the dash vents
- Ventilation system blows hot air all the time
- Ventilation system alternates between blowing hot and cold air (late-model 944s)
- The A/C pushbutton ("snowflake" switch) will not stay engaged
Water Comes Out of the Dash Vents
| Possible Cause | Checks | Procedure |
|---|---|---|
| Clogged HVAC condensate collection pan drain line | Behind the center console, there is a drain line approximately 1/2" in diameter that runs off the bottom of the HVAC unit and is routed into the top of the torque tube tunnel. Have plenty of rags handy before removing it — if the line is clogged, there will likely be a large amount of condensation in the bottom of the HVAC unit that will spill out when the line is disconnected. Remove the line and clean it. Also run a finger up into the drain at the bottom of the collecting pan to check for clogging there. Reconnect the line and ensure it is routed onto the top of the torque tube tunnel. | N/A |
Ventilation System Blows Hot Air All the Time
| Possible Cause | Checks | Procedure |
|---|---|---|
| Various causes depending on model year | There are several different problems that can cause the ventilation system to blow hot air, and the cause is dependent on the model year of the car. Refer to HVAC-01 for complete troubleshooting. | HVAC-01 |
Ventilation System Alternates Between Blowing Hot and Cold Air (Late-Model 944s)
| Possible Cause | Checks | Procedure |
|---|---|---|
| Dirty interior air temperature sensor | There is a small fan that supplies airflow to the interior air temperature sensor, located behind the small round vent next to the cigarette lighter. Follow that tube underneath the dash toward the firewall to locate the sensor. See HVAC-01 for sensor location photographs. Cleaning the sensor typically resolves this problem. | HVAC-01 |
A/C Pushbutton ("Snowflake" Switch) Will Not Stay Engaged
| Possible Cause | Checks | Procedure |
|---|---|---|
| Button latch has failed | Remove the temperature control unit and replace the pushbutton. The pushbutton is a separate serviceable part — the entire temperature control unit does not need to be replaced. Some dealers may indicate the pushbutton is not available or not separately replaceable; check with independent Porsche parts suppliers if the dealer cannot source it. | N/A |
Tags:hvacair conditioningheatingventilationcondensatetemperature sensor