Need failed Speed sensors

The new sensor is installed back in the car and is working great!

It looks like it was indeed a grounding problem. In my first attempt, when I tried to solder the ground tab on the board directly to the housing, the joint likely stayed "cold" on the housing side. Probably, when the brass housing heated up and expanded, the board lost its ground and the speedometer went dead. ... at least that's my theory.

After I removed the sensor again, I de-potted the board using a heat gun which softens the potting compound quite nicely. The blob pushed back out of the housing easily and I was able to strip the board completely of all of the potting compound. I then used a wire ground and repotted the board.

If anyone else uses one of these modernized speed sensor boards, before positioning the new board, I recommend first soldering a piece of uninsulated copper wire to the inside of the housing. I preheated the empty housing with my heat gun and was able to get a good solid connection between housing and wire using my fine-tipped soldering iron. (Is it an afront to my masculinity to admit that my soldering iron is inadequately small?). Once the housing cooled, I inserted the board (using 0 mm offset), soldered the other end of the ground wire to the board and repotted the assembly.

I must say this potting epoxy is good stuff. I am sure the new board will last forever because it is encased in oil-proof epoxy. The factory sensor uses gaskets to keep gear oil out of the assembly and that may be why they die as soon as they do. Disassembling, cleaning and potting the factory board probably (maybe) would make them last longer.

Thanks again for a cool project.

 

Hello,

I am reading all this great work that was done to make a new board for the 116987 sender unit! How can I get a board or refurbished sensor?

Great job!
Thank you!

Alex

 

Good evening
Would somebody be able to give me a little bit guidance on how to loosen up the speed sensor for my 83, 308 Quattro valve

They needed a wrench should be 32 mm however there’s not enough room to fit a wrench

If anybody has any feedback for me, it would be greatly appreciated.

Thank you very much

 

On my 2V GTB, with the inner wheel arch liner removed, it is very accessible. I've never tried to remove it with the liner in place, but can imagine that would make things tight. Below is a view of mine without the liner.
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Thank you for your feedback and the photo.
The the speed sensor is located in a different place, it is facing the ground, however I will take a closer look tomorrow and see if i can gain easyer access through the weel arch

Thanks.