Helag 2k2 - Potentiometer for M424 (Automatic heating system)

[petr916]

Hello together,
this is probably my first valuable input. This is my BIG thanks to all of you. I am using this source at least one year. My car description is deserving another thread. Maybe next time.

Today I want to share with you the way how to repair not functional HELAG 2K2 potentiometer. This part is very well visible on page 800-7 in Bentley's Service manual for 911 SC 1980.
In my case this part was completely blocked (sized) and measured value of resistance was like 80 KOhms. So my unit has looked death, even with proper voltage.

I have bought on ebay another HELAG 2K2 potentiometer, but shaft was shorter and it was missing slot for screw driver. (Hopefully my language is understandable for you, English is not my mother language).
So, I was forced to repair the original one. Fortunately the process is quite easy.



1) Remove the spring - on the both ends( seen in the middle of the main body)
2) Unplug the bottom lid
3) Remove the Circlip & washer
4) Push the rod & disassembly it from main body (take care about other washer on the rod)







After careful cleaning & lubrication of shaft I have reassemble all parts.
Proper adjustment of sliding contact point was necessary in my case.
Measurement of resistance is on the spot.




So, I am happy as my knob is really commanding the servo motor.

That is all this time.