NickWW wrote:Hi John
The answer to both questions is Yes
Kr's
Nick
Thanks for the answers Nick.
Referring to the first question ......... I find that very odd indeed. To have two complete instrument clusters misbehaving exactly the same way in the same car ...... very odd.
I am still of the belief that it is not the sensor itself as it is a passive unit whereby teeth passing in front of a coil wound around a magnet will generate a pulse per tooth pass. and referring to the second question, when the car stops, the pulses stop ...... but the speedo motor continues running. This indicated that some type of odd signal is being sent to the drive transistor to send it into thermal runaway.
This is going to take some time to resolve. My thinking is that it could be due to interference (electrical spikes) being induced onto the sensor wiring. But the first thing I would do is to make sure the screening around the wires from the sensor is earthed properly.
First I would check the earth points in both foot-wells. These are situated approx straight below the door hinges. One or both of these supply the earth to the instruments. Then I would check the sensor connector which is in a black box on the bulkhead just above the gearbox. See pic below :-
That three pin connector carries the signal x two plus the screen. That needs disconnecting, the female pins need to be tightened up and sprayed with switch cleaner ..... connected then disconnected a few times to scratch off surface corrosion, sprayed once more, then reconnected.
The other thing worth doing is to apply the same treatment to the female pins in the large connector on the LHS of the instrument unit. Those pins need to be as tight as possible.
If you want to have a go, let us know how you get on.
John
