So we disconnected the sender unit and tested it, same results (By the way it is putting out .10 volts, not 10 volts) We tested an Autometer sender I have, and it puts out whatever supply voltage is given it, in the correct square wave (this unit wont work on my cobra because of the rediculous cruise control sender projection, won't fit under the car)
VDO makes a sender that, according to a tech @ the VDO tech line, puts out a 16 pulse signal per mechanical revolution, @ 4 volts.. we are going to try that, I have one coming from
www.jegs.com ($49.95) certainly the cheapest part of this fix.
By the way, just in case you are correct, I am going to give the speedo it's own ground... it is ganged up now (By the way, I was formerly a R & D computer/electronics technician, and the in-dash wiring is not up to the kind of work I would want my name on, especially the crimp work and the too-tight/short wire lengths, but it's passable)
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