The '81 thru '93 with 14 pin connector store the speed digitally in a counter IC. I have yet to find a schematic for any year. They seem to be a little more reliable than the earlier 11 pin analog CC amps but not by much. They are not interchangable.

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Ron Schroeder
'85 300 Turbo Diesel 2 tank WVO
'83 300 Turbo Diesel 2 tank WVO
Some former WVO vehicles since ~1980:
'83 Mercedes 240D
'80 Audi 4000D
'83 ISUZU Pup
'70 SAAB 99 with Kubota diesel
'76 Honda Civic with Kubota diesel
'86 Golf
Several diesel generators
All with 2 tank WVO conversion
LI NY