Variable Reluctance Speed Sensor

[Guest chrispine]

Hi, I've got a ford van with a variable reluctance (VR) speed sensor on the diff, it "sees" the crownwheel teeth and sends a signal to the engine/gearbox management, which also drives the speedo, occasionally the speedo looses it's signal for a couple of seconds and the gearbox changes to neutral due to no speed signal from the sensor, I've changed the sensor, common fault it seems, but no change, the Haynes manual shows a grey wire from the management to the sensor and another wire coming back, I have a red wire to the sensor, with the ignition on I'm getting 1.45V DC, cannot find if I should be getting 12v here, afraid that if I put 12v where it shouldn't be I may trash the management, all the info I can find for VR sensors in general shows an input of 12v, does anyone know if I should have 12v here? Next step is an autoelectrician who is insured if they trash the management system.

 

Thanks in advance

 

Chris

[theduck]

VR sensor would normally have 2 wires to ecu (signal and ground) and possibly a shield aswell which just goes to ground, often also at the ecu.

Edited February 1, 2018 by theduck

[Guest chrispine]

Thanks mate, that makes sense (pardon the pun), signal and ground, surprised the cable isn't shielded though, will look at connectors next.

[Guest chrispine]

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Edited February 4, 2018 by crazy chris3rd