How do I get the "Automatic Heater" system to work on the 85 Carrera?

[jmod]

I came across the following data when trouble shooting the autoheat in my SC.

The Porsche Manual for the SC refers to the mirror sensor as being "1.5kOhm at room temperature". Bentley gives the value as 1.9k Ohm at 20C(69F).

The heat exchanger sensor is listed by Bentley at 1.7K Ohm at 20C (69F). The Porsche Manual lists the value for the exchanger sensor at 135 Ohm at 100C (212F).

It may be possible to find standard thermistors that are close to these values.

[markmalin]

Originally Posted by jmod

I came across the following data when trouble shooting the autoheat in my SC.

The Porsche Manual for the SC refers to the mirror sensor as being "1.5kOhm at room temperature". Bentley gives the value as 1.9k Ohm at 20C(69F).

The heat exchanger sensor is listed by Bentley at 1.7K Ohm at 20C (69F). The Porsche Manual lists the value for the exchanger sensor at 135 Ohm at 100C (212F).

It may be possible to find standard thermistors that are close to these values.

Thanks!! This is very valuable information. I'm sure it would be possible to find a stock thermistor somewhere that would give these same readings.

Mark.

[javadog]

Originally Posted by markmalin

So if I can find a used manual setup with only one lever, I don't have to buy new cables? Or will I need different cables/sleeves anyways if I convert my automatic heat to manual setup? I'm just about to pull the trigger on ordering a new cable (dual cable) and 2 new cable sleeves (guides) for the automatic system.

Porsche has used single cable and dual cable systems at various times, so you could use either. The single cable actually uses the same guides as the dual cable, since you have to have a wire going to each flapper box. The difference is at the end where the cable(s) attach to the lever(s). I prefer two levers, as then the heat can be adjusted separately on either side. Note that several different wires have been used over the years, so buy the one(s) that is(are) for use with whatever controls you end up deciding to use.

Sorry to hear about the sensor. I figured it was a long shot but worth checking.

JR

[javadog]

Originally Posted by intakexhaust

From memory, I think it changed late 86 for the 87 model year bigger vents and the sensor in the dash.

The 1986 models had the revised sensor location and the bigger dash vents.

JR

[CVJR]

After reading the posts today I tackled my inoperative auto heat this afternoon (Federal holiday). 40 degrees today in the MD/ DC area, so great for getting heat to work.

My passenger seat came out very easily, although watch for the backing pates to fall to the floor. I used a magnet want to fish them out. Turns out the clevis on the front end of the rod was broken. Broken because the cables were very stiff. I confirmed this by moving he cable belcarank manually. I was able to tie wrap the clevis end so that it stayed (mostly) on the ball stud long enough for the heat to come on while holding the clevis against the belcrank connected to the heater cables.

Next, I got the car up on a lift and sprayed some PB Blaster on the cable ends under the car and worked the cable back and forth some as best I could. I need to clean and or replace the cables, but at least I now know the auto heat unit is function. On the way home from the lift, auto heat worked, including the max "shoe melt" setting. I'm pretty sure the rod clevis will pop off again soon, so I'll get a couple of those too and leave teh right seat out for now.

Thanks to all for the advice.

[CVJR]

Forgot to include a picture for reference. CV