Joined: 26 Apr 2018
Location: Austin, TX
|Posted: Sat Apr 28, 2018 11:49 pm Post subject: Wiring question for coolant temp sensor (ground wire)
|Hi, I am the guy with the high reading coolant temp sensor (and the bouncy speedo as well).
Finally I actually took a look under the hood, and whatya know, I discovered that the one of the previous owners had swapped out the 2 pole/blade sensor for a single pole/blade version (where the second pole/blade is replaced by the metal sensor body acting as the ground path on the engine once it's screwed in).
As an aside my ' 73 911 has such a single pole for the brake light switch, which is actually a hydraulic pressure sensor on the master cylinder rather than a mechanical switch at the pedal like most other cars. I always wondered why it didn't have a second blade: now I understand.
Anyhow, it is all coming back to me now. I recall that the previous owner mentioned something about the temp gauge reading hot because of a ground issue. This must be it.
I am sure that whatever single pole temp sensor whoever did this found at autozone is not calibrated the same as the correct Bosch 2 pole version the car is meant to have and this explains the readings
As I am an "Anal Andy" that hates kludged-up fixes, I am going to try and troubleshoot/fix that bad ground wire and put back in a 2 pole temp sensor as well as as the corresponding pigtail 2 pole connector.
So finally to the question: does anyone have any idea where that temp sensor ground wire runs in the wiring harness and to which ground point on the chassis it goes as I'd like to follow the harness along the same route and terminate at the same chassis point?
Thanks in advance for any responses.