TS-10, Troubleshooting - Heating, Ventilation, and Air Conditioning (HVAC)

Introduction

This troubleshooting guide is intented to help identify and repair heating and air conditioning problems. The following is a list of problem symptoms discussed in this guide:

Water comes out of my dash vents.

Possible Causes
Checks
Procedure
Clogged HVAC condensate collection pan drain line. Behind the center console, there's drain line approximately 1/2" in diameter that comes off the bottom of the HVAC unit and is routed into the top of the torque tube tunnel.

You're going to remove that line and clean it. But, before you do make sure you have plenty of rags handy. If the line is clogged, there's likely a lot of condensation in the bottom of the HVAC unit condensate collecting pan which is going to come out when you remove the drain line. Remove the line and clean it. Also, run your finger up into the drain on the bottom of the collecting pan to see if it's clogged.

Reconnect the line and make sure it's routed onto the top of the torque tube tunnel.

N/A

My ventilation system blows hot air all the time.

Possible Causes
Checks
Procedure
There are a number of different problems which can cause the ventilation system to blow hot air. The cause of this problem is dependent upon which model year car you have. To troubleshoot this problem refer to HVAC-01.

HVAC-01

My ventilations system alternates between blowing hot and cold air. (Late Model 944s)

Possible Causes
Checks
Procedure
Typically this is caused by a dirty interior air temperature sensor. There is a small fan that supplies air flow to the interior air temperature sensor. It's located behind the small round vent next to the cigarette lighter. Underneath the dash follow that tube toward the firewill and you'll locate the interior temperature sensor. See pictures in HVAC-01 for sensor location.

HVAC-01

The A/C pushbutton ("snowflake" switch) on my temperature control unit will not stay engaged.

Possible Causes
Checks
Procedure
Button latch has failed. Remove temperature control unit and replace pushbutton. The pushbutton is still available but many Porsche dealers will tell you it's not replaceable and that you have to replace the entire temperature control unit ($$$$). They may also tell you that the pushbutton is no longer available. If so, try Pelican Parts. I believe it's still available through them.

N/A

Clark's Garage 1998