How to test a speed sensor?

[jay8086]

Does anyone here know how to test a speed sensor? What voltage should I be getting on which pins of the car wiring and is there a way to see if a replacement sensor functions before fitting it to the car?
Any help would be great coz I need a working speedo.

[jay8086]

Ok, so far i figured out that the speed sensor is a hall effect sensor with 12v input, and the output drops from 12v depending on speed. Can anyone confirm which pin is 12v input and which is output.
My other question is looking into a replacement sensor / pinion / tachometer screw there appear to be 2 to choose from. The sensor has only 1 part number but there are 2 numbers each for the pinion and tachometer screw. I've noticed as well that there is a pinion with a black cog and another with a grey cog. Is that the difference in part numbers? Is there a physical difference between the black and grey cogs? And must a grey cog be replaced with a grey cog and black with black?


Thanks for any help

[cully]

autodata info on Vss


  vss.pdf (Size: 23.02 KB / Downloads: 19)

[jay8086]

Thanks for the autodata info. I had a look and it says that pin 1 is battery voltage and pin 2 is earth. The wiring diagram in the haynes manual says that pin 3 is battery voltage and pin 2 is earth. The connector on the sensor also has numbers 1 to 3. Knowing how accurate the rest of the haynes manual is i'm guessing the autodata info is right but can anyone confirm that if you go by the numbers marked on the sensor that pin 1 is battery voltage, pin 2 is earth and pin 3 goes to the instrument cluster / speed dial.