On board computer temperature sensor

[Kibokojoe]

After studying the electrical trouble shooting manual I have found that there is only one sensor that displays the temperature on the "on board computer" obc. This is located on the driverside down near the fog light. So if the obc is reading -35F then the sensor is bad or I have a break in the wiring. Is this correct? 1989 535i

[shogun]

Yes, sir, that is correct.

[Kibokojoe]

Found the broken wire. Traced the sensor back up to a 6 to 8 pin round connector. Pull the wire ties holding the rubber boots on and found that one side was totally corroded. Two wires fell free immediately. Now my question is how do I get this connector apart? I have tried twisting it and prying on it but nothing seems to give. It looks like you should be able to just spin it apart but it wont budge.

[Kibokojoe]

I tested the sensor and it ramps up and down when I put some heat to it.

I finally got the connector open and it was oxidized big time. As a matter of fact the connector on the sensor wire blue/red was completely oxidized away. The connector was so messed up that I just cut it off and soldered the wires together. Turned on the car and got -29F crud..... Well at least it is not a negative 35F anymore. I think the wire is probably ruined all the way to the on board computer. Since we are working with ohms here any oxidation is going to through off the reading. Does this seem logical?

Ken

[shogun]

Wait for hours, the temperature goes very slowly back to normal.
Maybe tomorrow it will be correct.

[Kibokojoe]

This morning when I started the car the OBC was blinking DATE over and over. I pressed the temperature and it came up 65F. Very cool. I noticed that it was very difficult to solder the wiring. Is there some kind of protective coating on the wiring? If so how do you get it off? Acetone?


Thanks for you help

Ken

Wait for hours, the temperature goes very slowly back to normal.
Maybe tomorrow it will be correct.

[shogun]

How did you know

Because that question comes often, people still believe their sensor is defective, but it goes slowly back to normal

Is there some kind of protective coating on the wiring? If so how do you get it off? Acetone?

No idea, I believe it is just a normal wire.