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Discussion Starter · #1 ·
Looking for wiring schematics for the VSS on a 1990 W250. Recently finished up a 440 swap. Speedo and odometer don't work, began with sporadic speedo needle movement before quitting completely. This issue began long before the engine swap. The small block came out around 8 years ago. Life, ya know? I've got pulses from the (new) vss, but nothing at the speedo. That is assuming I can test between the vss input at the gauge cluster and the cluster ground in the same way. I have continuity from the white/orange wire at vss to the sensor input at the gauge, however I did not have 5v at the vss connector. Couldn't find any breaks in the ground wire up to the connector on the firewall. I've read in some threads that the wiring goes through the ECM, from what I remember mine has been unhooked for years when I converted back to a carb from TBI. I've also checked the vss drive gears. This is the last piece of the puzzle to have everything working, it's driving me up a wall.

Tire Wheel Cloud Sky Vehicle
 

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You have the first year of the electronic speedo. Quite possible the little plastic gears in the speedo head are stripped. They sell them on ebay.
 

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I had roughly the same problem - bouncy until about 40MPH. Checked the VSS etc, turns out it was the speedometer. Here's the diagrams you may find useful.
 

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Sorry they're upside down :(
Stupid technology
 

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Discussion Starter · #7 ·
what he said above is the most likely problem , the diagnostics below checks the wiring out

Thank you, sounds like I'll be calling some junkyards. I had another to try but ended up breaking it trying to put the needle back on. Made me hope I had missed something for an easier fix
 

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Thank you, sounds like I'll be calling some junkyards. I had another to try but ended up breaking it trying to put the needle back on. Made me hope I had missed something for an easier fix

post # 2 Jerseybud / it's most likely the GEARS and there is a howto change them

 
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