Speedometer Sensor Replacement

[Don Ivey]

My '87 Carrera had both odometer and speedometer stop working at the same time, and after looking at the Bentley, I believe the sensor is the culprit. Does this make sense? I would assume that if one or the other stopped working it would be a guage problem, but not both. Any thoughts? Thanks,

Don Ivey
'87 Carrera
Raleigh, NC

[86 911 Targa]

Give North Hollywood Speedometer a call @ 1-818-761-5139.

[dentist90]

Not sure if the G50 uses the same style of magnetic pickup as the 915, but if so you could check to make sure the sensor is properly in place and that the wires have not been damaged or pulled apart at the tunnel.
To test it's function you would probably need an oscilloscope, I'm not sure a volt meter would pick up these minute pulses.
Hopefully someone has experience with this. The sensor on the 915 is very easy to replace, can't comment on the G50.

[toddu]

Originally Posted by dentist90

Not sure if the G50 uses the same style of magnetic pickup as the 915, but if so you could check to make sure the sensor is properly in place and that the wires have not been damaged or pulled apart at the tunnel.
To test it's function you would probably need an oscilloscope, I'm not sure a volt meter would pick up these minute pulses.
Hopefully someone has experience with this. The sensor on the 915 is very easy to replace, can't comment on the G50.

Not to hijack -
When connecting, the wires aren't color coded. Does it matter which way they connect in the tunnel?

I put a new sensor in, and it randomly works. Need to check that the "puck" is still seated fine. Would think if it were reversal of wires, it just wouln't work.

After the fact I hacked out a bunch of wiring (radio delete), so might have dorked up a ground or something too.

Todd

[dentist90]

If it does matter I've been lucky the several times I've had it disconnected to get it back together the right way. I don't think it would cause any harm to reverse the wires and see what happens. I just assumed one was for the speedo and one was for the odo.

[KTL]

I just connect the same color wires to each other in the shift coupler access in the tunnel. I never checked to see if it works with them connected via different colors. I've noticed that the magnets in the speedo sensor ring can collect metal filings over time, so it might be worth it to clean off the buildup of metal sludge on the sensor ring. You can rotate one of the wheels with the car in neutral and wipe off the ring thru the sensor hole.

The G50 sender is not the same type as the 915. So don't go looking for a used 915 sender to see if that fixes it! The both do the same thing, but for whatever reason, Porsche changed the sender on the G50. There's actually a TSB from Porsche on the original sender.

[KTL]

[dtw]

Originally Posted by dentist90

Not sure if the G50 uses the same style of magnetic pickup as the 915, but if so you could check to make sure the sensor is properly in place and that the wires have not been damaged or pulled apart at the tunnel.
To test it's function you would probably need an oscilloscope, I'm not sure a volt meter would pick up these minute pulses.
Hopefully someone has experience with this. The sensor on the 915 is very easy to replace, can't comment on the G50.

The 915 sensor can be tested with any cheapo analag test meter on the resistance/ohm setting. I don't believe the orientation of the wires matters on installation.

No idea on G50, sorry.