Vehicle Speed Sensor

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smtguy
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Vehicle Speed Sensor

Post by smtguy »

Gentlemen,
Does anyone know where the Vehicle Speed Sensor is located on an e24 and how to test it?
Thanks,
Scott
1983 Bronzit 633CSi 5 speed
2004 Audi TT Quattro 6 speed

Scott
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hornhospital
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Re: Vehicle Speed Sensor

Post by hornhospital »

On the second generation E24s (after mid 1982) it's in the back of the differential. It's a pulse generator. I don't recall exactly how to test it, but I know they seldom fail. It's usually the wiring that breaks.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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smtguy
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Re: Vehicle Speed Sensor

Post by smtguy »

Thank you Ken.
1983 Bronzit 633CSi 5 speed
2004 Audi TT Quattro 6 speed

Scott
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Brucey
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Re: Vehicle Speed Sensor

Post by Brucey »

the sensor in the diff is a reed switch type device. It 'reads' a toothy wheel inside the diff. With the car jacked up the sensor should measure either open circuit or dead short on a DMM with a 50% duty cycle, changing several (eight?) times per wheel revolution.


IIRC with the ignition on, measuring at the diff sensor connection, one of the two harness wires should read +12V and the other one should have a measurable impedance to ground

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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smtguy
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Re: Vehicle Speed Sensor

Post by smtguy »

That's what I was missing.
Thanks Brucey.
1983 Bronzit 633CSi 5 speed
2004 Audi TT Quattro 6 speed

Scott
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hornhospital
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Re: Vehicle Speed Sensor

Post by hornhospital »

That's what I couldn't remember. If it was a reed switch or a Schottky device, and how to test it. Thanks Brucey!
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
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