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This is my first technical post on this forum in a while.
We have a 1983 Euro spec 911 SC that we acquired about 4 years ago. I do all the work on it myself. One of the last things to tackle after getting the car mostly sorted was the heater control. The potentiometer that sets the temperature for the automatic system was seized. After freeing this up and confirming that it still worked, i discovered that the system would only go to full heat. This was due to the interior temp sensor behind the rear view mirror being broken, most likely due to a windshield removal that happened before I owned the car. Pelican parts says the sensor is no longer available and did not offer an alternative, and I could not find any information on this topic on various forums.
So, I went to MIcro- Center and purchase a variety pack of different resistors for 11.50$ to try and replicate the sensor. The manual says the sensor should be 1.9 k ohms at 68 F. After installing that in place of the temperature sensor I found that system worked but I did not have the full range of the motor that moves the heater lever, only the last 30%..
After experimenting with different resistors, I
found that a 1.2k ohm resistor worked perfectly, giving me the full operating range, with position 5 being fully open, or maximum heat.
I hope this helps other with he same issue with their automatic heating control system.
I had a similar experience with my 89 different but similar inputs. But n mine it was a failed temp
Sensor in the exhaust. Interior sensor was fine. That simply tells the car to open full until it’s warmed up. It was broken and open so it caused auto heat to be full all the time. Putting a resistor on it allowed fully variable control. I used a variable resistor aka potentiometer to find the right value.
I've got a similar issue with my 69R taillight conversion. The bulbs use a different wattage than stock bulbs so the blinker speed is too fast for my liking. Guys have said "we all just add a resistor" but who-what-where?????? Fun problems to have.
12-31-2017, 01:52 PM
911 SC Heater control temp sensor
