Al Z

Hello
I just purchased an 87 Turbo, previous 993 owner. The heat does not work on it. It has the automatic heat control dial in between the seat, but it does not have the heat levers on either side of the hand brake. Is this correct? or does the automatic heat dial control the heat function... Any suggestions. Is there any fuses for the auto heat control dial I can check? Thanks in advance..Al

A930Rocket

I have an '87 also and it's done automaticaly by the dial. Or at least it's supposed to.

On one side or the other of the dial, there is a panel you can remove and look into. There was a tech article somewhere that explained what can be done to correct it. Maybe a search will bring it up some where.

It would be nice to have the emergency side lever like I did on my '81 SC with auto heat. Maybe it can be retro-fitted. Probably cheaper than to buy new parts to fix.

Good luck.

justkickenit

I have an 88 930 and I do not have the levers either. These levers are on SCs and models w/o the
automatic temperature control.

jhunt@huntinter

You can retrofit an earlier version easy enough. My '79 has the requisit **** as a point of reference. Everything is the same except for the little red **** sticking out.

Al Z

Thanks everyone. I was not able to locate the tech article on repairing the auto heat dial... does anyone have a link? Does the auto heat dial just open the flaps for the heat boxes? Thanks again...

jhunt@huntinter

Think of it this way.. since this is how the Porsche engineers worked it. Take a early (non automatic car), build a plastic box with a **** and a motor, connect motor to the old red ****, then based roughly on temp, have the motor pull the **** up and down for you to try to keep the temp in the car roughly equalized. Later models cut the red **** off, so they wont have any way to activate heat when the motor breaks.

BTW: Often what fails is a small circuit board (2" by 3"). This is an example of high tech back then, but today most of us could probably fix it with parts from radio shack and a soldering iron.

Al Z

Hello jhunt
Could you tell me where the circuit board is loacated.. do you have any pics of the board or how to repair it.

MitchB

I don't think the automatic system is quite as simple as that.
I've done a bit of research on these buggers and here my thoughts.
The auto system was introduced on the turbos before the SC's - I assume as a more modern "flagship" upgrade. It does more than thermostatically control the heat. The last three hottest posns also turn on the fans in the footwells that pump up the defrost function.
That portion of the system doesn't work in my car. I have tried to trouble shoot that def boost system (it has never worked) on my car and have determined the fault is in auto heat controller. I've had it out and completely apart. To fix it would require replacing the box or an alternate switch. I'll wait and find a good used controller.
The thermostatic control of the heat, however works flawlessly. Set it and forget it. I would never take it out to go back to the old manual system.
I like it.

jhunt@huntinter

Start by just removing the whole mechanism from between the seats (it's just four or five bolts). Then you will see all the parts, you can even test it a bit and see what is or isn't happening. This is a simple piece of machinery. The circuit board is inside and is accessed by popping off one of the side panels. It is a motor, a reduction gear to give the motor some torque, and a circuit board to read the thermostats and tell the motor to go up or down, that is it.

It is wired to power and the little thermostat that hangs above the rear view mirror (ok, maybe a couple of more thermostats by the heat exchangers and on later cars a relay for some footwell fans also). It has to be able to constantly adjust itself because when you get on boost your car produces a lot more heat. So to keep the inside temp stable it has to close the vent a bit and vice versa.

BTW: Mine is a '79 and does not have footwell fans or a defrost booster. I don't think any had defrost boosters, but later models did have the footwell fans. Normally aspirated 911's had a fan booster in the engine bay, we don't because it didn't fit.

jhunt@huntinter

Here is the super dee duper high tech circuit board..

jhunt@huntinter

The little motor...

A930Rocket

My '81 SC (euro) had the automatic control and the red ****** lever. As the auto heat didn't work, I had back up at least.

The thermostat was behind th erear view mirror. On my '87, I dont have that same thermostat, but have one on the dash board, just to the right of the steering column. At least I think that's what that is.

paulleslie

I know this answer is years late ,but may help , .There is a sensor attached to the engine which controls the heating on and off .When engine cold the sensor prevents air being drawn into cabin and keeps fans off ,as engine heats up after 2 to 3 mins this sensor allows fans to work and vents to open ,only in the auto heat system post 1986.
Cutting this white covered sensor wire where it comes into the car over the tunnel between and behind the front seats allows system to come on , or get a new sensor.
May be the cause of most auto heat failures.
You will see this sensor in the wiring diagrams.
Good luck

3.6conversion

glad this ithread was resurected. my 79 has the auto heat w/ the single red level. when i turn it on the lever will move automatically and i can feel warm air/heat but the blowers do not blow the air. also the control **** turn very freely and does not have any defined stops point/notches like the manual controller i have in my 88 911 w/o auto heat.

911rudy

STOP! Before you jump into all of the hard stuff do the easy stuff first. My '87 did the same thing and it turned out to be, you guessed it, a small piece of PLASTIC. Those magnificent Krauts had a propensity to use plastic whenever they could on little parts that were considered lifetime parts. The little mechanical linkages are in the center console has two heim joints like the old carburetor linkage except instead of using brass ends like the carb they used two little plastic ends. The picture above of the motor end shows the little male heim stud but not the piece that is part of the car. They are designed to fail if rust and crud get into the two heat valves below the car and become hard to move. That little link does the same job as the little lever on the old SC. On my car the plastic end broke and I put a Holley carb ends on it and cleaned the heat valves. Do yourself a favor and remove the passenger seat and then it will be really easy to get to it. If the link is intact unhook one end and see if the little motor will move the motor end arm. If not ,THEN start with the circuit board crap AFTER you verify that the little motor is ok.
If anyone can figure out a way to hook a little lever to the reward end of the link then you can always have a manual back up if the electric, er that's when the electric fails.