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Thanks. I have a copy of Bentleys also and did a little research late last night. Had to get my magnifying glass out to try to make out the notes on the wiring diagram. Seems that there are some inconcistancies with the diagram and item index for the diagram. Looks like +12V is supplied on the blue wire, the black wire is ground, and the other wire (striped, but can't remember the colors) is the signal input the the speedo.
I did a little research on the internet for information on magnetic reluctance sensors. I presume this is the type of sensor in the rear end based on the little info I have. If anyone knows otherwise please advise. Anyway they act very much like an electric guitar input ---Magnet, ferrous core, and coil of wire wrapped around the core. As the ferrous sensor wheel interrupts the magnetic field it induces a current in the coil of wire. Anyway given time this weekend I will try to build a simulator with a sine wave generator, small inductor, and a resistor and feed it into a speedometer on the bench. Can't tell for sure if any of the rest of the cluster but it seems that the speedometer assembly may be self contained. I'll have to look more closely -- maybe a ground wire is needed to power the circuitry on the speedometer.
General operating theory for this type sensor is to feed the signal into an amplifyer and convert each wave to a pulse. I read elswhere on the board that this pule trane is integrated into a variable DC current dependent on the speed. This current is fed into a coil which generates a magnetic field field proportional to the frequency of the pulse trane. This magnetic field acts on a magnet which moves the pointer. The more pulses, the higher the current and the stronger pull on the magnet. I assume that the motor for the odometer is "stepped" by the same pulses.
Sure would be nice if someone "in the know " would add to this discussion.
Dan
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