Speedo / Odometer erratic and inop—-> VSS alternative solution

[caddywompus]

My speedo was on the fritz for months so asap I did the logical thing and replaced the VSS with a used one—including pinion gear which looked fine—that I had around thinking quick easy solution. Well that didn’t work so then I bought a new one: P/N: 357919149 No change, same result speedo widely fluctuating, ODO correspondingly recording erratic mileage. So then I dug deeper into the parts bin and tried a variety of VSS / pinion gear setups but still no change, dead speedo. By this point all signs were pointing to the cluster and I had a couple spares to try, but life got in the way so I shelved this and lived with it for months and lived with a simple/cheap 12v satellite MPH gauge suction cupped to the windshield for the better part of a year.

Passat/Jetta VSS units with longer pinion gear but same electronic sender at the top;

Finally I found the time to dive in and swap clusters. Which BTW can be done w/o removing the steering wheel and dealing with the airbag. The first one a diesel Euro one I’ve been itching to try out. No dice, same prob. The second one a US 97+ gas one but no change, speedo still dead.

By this point I was pulling out my hair and really dreading diving into testing the wiring but I really wanted to see my odo flip over to a huge upcoming milestone: 500k miles.

Part of PITA with diagnosing this particular system is though the VSS isn’t particularly difficult to remove it is in an awkward area of the trans and not exactly fun to keep crawling under and installing/removing/driving after each progressive level of the Dx process and that’s when I had this idea for testing in situ:

[youtube] https://youtube.com/shorts/E4WF4l2ShS8?feature=shared[/youtube]

That made testing the wiring much simpler and quickly I discovered the culprit: damaged/chaffed wiring harness by exhaust downpipe. Easy repair with the replacing the damaged section and thermal insulating well and securing along its route. Hopefully this helps someone before they pull out all their hair or spend an obscene amount of $$ for this pesky prob.

Justin
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Eurovan TDI Syncronaut