testing speed sensor
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Joined: Dec 2002
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From: Australia
You could also do it at the plug in the spare wheel well, as thats the nearest connector. I doubt the sensor has failed - its just a reed relay triggered by 8(9?) magnets in an alloy ring bolted to ring gear. Most of these issues are wiring related - start by checking the spare wheel well connector is clean and bright. Then check for make/break at the central board. After that , wiring to the pod - the connectors that carry leads into the instruments may need cleaning, and bending to improve contact - mine did!
jp 83 Euro S T 54k
jp 83 Euro S T 54k
Nordschleife Master
Joined: Jun 2006
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From: ɹəpun uʍop 'ʎəupʎs
My 87 was missing it.. just two bare wires by the rear of the diff housing, and no sign of the sensor, M6 bolt or wire hold-down
Instructor
Joined: Nov 2003
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From: Dorset
No Glenn, the magnets are in an aluminium disc bolted onto the side of the diff, (opposite side to the ring gear), see picture page 39-8 of WM. And John, you shouldn't say alloy to indicate ally.
Smiffy
Smiffy
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Racer
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i did check the connector in the tire well and it looked ok if it's the right one.it had the shieilded wire along with two browns if i recall correctly.3 pin connecter.yes i did rebuild the diff and cleaned the magnetic pickup.and reinstalled the sensor to the back cover.it did not work before that either.any other suggestions to try and trouble shoot speedo and odo?thanks
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From: Buckeye, AZ
In the 1990 PSD, the magnet disc can come loose - I've seen it happen. The sensor itself and the rest of the circuit tested good by taping some magnets on a sanding disc and using that with my electric drill to simulate the magnet disc. The faster the drill rotated the magnets by the sensor, the higher the speed readout on the instrument panel. But the rotating diff itself would not send a signal. When we opened the diff, we found the magnet disc was completely loose. In 1991, the speed sensor was moved to one of the front wheels.
In the earlier diff like you should have, the magnet disc is "pinned" on the right side of the LSD. I don't know if the disc can come loose like the 1990 PSD can. If you get no response from Colin's original test suggestion, you might figure some way to simlate the disc operation like I did.
In the earlier diff like you should have, the magnet disc is "pinned" on the right side of the LSD. I don't know if the disc can come loose like the 1990 PSD can. If you get no response from Colin's original test suggestion, you might figure some way to simlate the disc operation like I did.
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From: Tasmania, Australia
Time to test the output as Colin has suggested. Check at the closest point to the sensor output (at the connector in the wheel well) and go from there back up the line.
Establishing output has to be your first test.
Establishing output has to be your first test.
