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Discussion Starter · #1 ·
1990 Bentley Turbo R.
I was driving at highway speed and the speedometer needle started bouncing erratically for about 30 seconds and then quit completely.
Is this an electronic speedo, or is it connected by cable to the trans?
Any troubleshooting steps will be appreciated. Thanks.
 

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This is definitely an electronic speedometer and your issue sounds like a classic sender issue.

The first thing I would do is check to see if the sender has somehow experienced an incursion of water and some corrosion. You can sometimes fix this by simply doing a good cleaning, deoxidizing, and thorough resealing of the sender encasement.

If that is the problem, but cleaning doesn't fix it, here's another viable solution from another Turbo R owner who experienced the same problem you're having: A stock item for GM transmissions, “Hall Effect Speedometer Sender”, part No. 5291, 16 pulses/rev, 7/8” thread, about $70 depending on vendor. See egauges.com, or any of a number of online sources. It’s a perfect fit, but you have to splice in a new three-wire connector plug.
 

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You wouldn't happen to know of a replacement oil pressure transducer for a 99 Seraph would you? $800 seems a bit high to me.
 

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Oilpressure sender

Isn't this about the BMW V12-engine? Maybe you check out in this area, must be not more than 40 Euro in my opinion.
 

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Discussion Starter · #6 ·
Thank you, disassembly and cleaning worked perfectly. Does this sending unit also provide the signal for the cruise control? Thanks again.
 
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