Intermittent speedo

[Uponblocks]

Hi all,
My 92 964 C2 tip has developed an intermittent speedo both analogue and via the digital display.
Seems to be very random but exacerbated by potholes and bumps!
I,ve read a ton of forums/ threads which suggest ABS sensors, relays or mechanical failure within the speedo itself, but any ideas where to start?......I.e is there some simple checks I can carry out ?
Seen a similar thread on the 993 forum suggesting sending off for refurbishment, but would like any sensible suggestions as to root cause first?

Thanks in advance

 

[mcgc0]

If a Tip (regardless of MY) then the speedo takes it's input signal from the wheel speed sensors - via the ECU. Rough road conditions could indeed be dirty/loose wheel speed sensors - easy enough to look at and check. But could also be an intermittent or loose earth - are any other instruments playing up a bit? The instrument earth point should be left side under the dash/windscreen. Can't recall if actually under the dash or accessed from the front boot and under the windscreen corner.

Failing all that see if you can borrow another (working) speedo and plug in, that will eliminate external effects.

 

[Uponblocks]

Thanks for the reply.
One question.....are there 2 speed sensors or just the one? If one , which side is it located on?
Cheers

 

[T911UK]

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