84 Vanagon

Two weeks ago I lost my dash lights and coolant gauge.

Two days ago I lost my speedometer and odometer at the same time.
Over 200 miles, they flickered on briefly numerous times, meaning
I saw the speedometer needle twitch, and cumulatively over the 200
miles the odometer logged about 2.  I've already examined the speedo
unit and can find nothing wrong.  

Ideas.....

4 weeks ago I pushed the oxygen sensor reset button

Yesterday I sealed my leaky windshield..... 

Today I ripped apart the dash looking for electrical troubles.  There was
lots of corrosion on the ground connections behind the fuse panel.  Once
I cleaned that up, the dash lights came back.   But not the speedometer
or odometer.  

Could there be some simple thing wrong with the cable or its 
connections?  How can I tell?

Steve E
Vanagon 84
Lansing Mich

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