Q – My 86 930 Turbo has been the joy in my life and a curse. I still love it though I am freezing. I took it in three times complaining of lack of heat but got nothing except warm feelings. The problem is, the feelings only last until I get to the end of the driveway then I freeze again. Help. Ron
A – These older heating systems are tricky. But analyzing why you have no heat is simple. You have two heater control boxes attached to the body on either side of the transmission. When you need heat, two cables, attached to the electronic heater control module between the seats, open the valves, turn on the fans and viola’ you get heat. What could be simpler?; certainly not this system.
The most common failure is the linkage coupling in the module. It is cheap and so easy that I am sure they have already looked at it. Since Porsche was trying to make the system sophisticated they added a sample motor to monitor the cabin temperature, heat sensors at the control boxes to monitor the heat temperature, a circuit board to sort it all out, then a servo motor to convert the input into output. Oh and I should mention the numerous fans that distribute or boost the flow.
The time consuming part is figuring out which component or component(s) have failed. For that, I use a test car (borrowed with permission of course” to compare inputs and outputs which are poorly documented in the service manual. Then, again with permission, component swapping takes place. Why not just replace what you think is wrong? The parts cost alone can top $2,000 for genuine Porsche parts if you simply fire the “parts cannon” at it. So one must proceed cautiously when spending some one else’s money.
I am certain that if you take this approach, you will have heat again, fall in love with your “beast” and take it out on cold November days without frosted toes. MC