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spuggy spuggy is online now
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Join Date: Jul 2003
Location: Perfidious Albion
Posts: 4,184
Quote:
Originally Posted by ant7 View Post
under the impression that the sensor was actually similar to the Crank reference sensors
The "sensor" is a reed switch. It's open (infinite ohms) when there's no magnet under it, and closed (no/low resistance) when there is. One side is power, the other is a square wave fed into the speedo, which counts the pulses.

Quote:
Originally Posted by ant7 View Post
try turning the wheels to a different position, and see if I get anything different
  • Get a helper to turn the axle or wheel. Or roll the car - doesn't need to be in gear.
  • Measure continuity.

But if the wheels are off the ground and you have an open diff, make sure to turn the side with the sensor/carrier disk...

Turning the axle and randomly measuring continuity statically is the hard way to do this.

Dynamic test is much better & easier - one full turn and you'll know exactly what's going on.

Rolling diameter of the tire is ~25", so the car doesn't need to move very far. When I was calibrating my Yellow Dog, I checked the sensor for correct operation by sticking a leg out the door and scooting the car backwards Flintstones style.
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'77 S with '78 930 power and a few other things.

Last edited by spuggy; 05-08-2025 at 08:57 AM.. Reason: add reed switch comment
Old 05-08-2025, 08:46 AM
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