testing speed sensor on g-box

[richman711 10]

Hi guys

 

Looking for any method to test the speed sensor? ( and wiring for that matter).

 

Basically my speedo some has started jumping all over the place randomly, seems to play up mainly at 60mph+. I was doing 80mph earlier ( private road officer) and the speedo was reading well past 160 and then back down again.

 

Any way I'm guessing some one has had a similar fault?

 

Cheers

[fendervg 33]

What car do you have? I think some are electronic and some cable driven?

 

The family album shows two different systems - gear driven by a cable from the gearbox up to chassis # 50-L-035 000, then electronic after that. The electronic version uses a two-pin sensor. My guess is either the cable is old and is sticking (WD40?) or you need to check the wiring and earths for the later system.

Edited September 15, 2015 by fendervg

[richman711 10]

Cheers for the help:)

 

Mine must be a later type ( it's a 91 g60) as it's a sensor that screws straight in the gearbox with a 3 pin plug to it.

 

I've had the sensor out and the gear drive is fine with no wear (not sure about inside the box tho), so I presumed it was either the sensor is failing to send the signal? Or wiring fault. Any one know what pins on the plug are live and earth?

 

Cheers

[fendervg 33]

Test it with a multimeter - try on the plug from the loom first - I'd say one wire is 12 or 5 volts with the ignition/engine on, one is an earth, and the other one for the fluctuating signal back to the speedometer. Usually the outside pins are voltage in and earth and the middle signal, but I could be wrong. What colours are the wires? I don't have any wiring diagrams handy at the moment. Earth is usually brown or brown and another colour.

 

Your sensor is probably part#191919149D, the others seem to be for automatics and for the VR6.

Edited September 15, 2015 by fendervg