Another Speedo Thread (i've Searched) - Wiring Question

[shaodome]

After getting ABSOLUTELY ZERO responses over two weeks on CL , I found this forum and figured maybe somebody here would be kind enough to lend assistance.

I'm going to combine my thread on CL located here, so as to not make a bunch of posts for the same issue. I am pretty much at a total loss of where to go now...I do have access to an O-Scope, but I was trying to lug that beast out...circa 1978..ha.

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Ok, so I am still making my way through this wiring mess of an SC300 I picked up recently. The speedo is dead in this car, but it doesn't appear to be a cluster issue as I checked it by changing it out for a known good one...no dice.

The previous owner told me the speedo sensor was changed....but he also said the car had a R154 Soarer (which it DOES not). I put the car up on stands to investigate and did see some wiring done at the speedo sensor on the rear/driverside of the W58 trans. Looks like an aftermarket replacement as there was no plug and both wires coming out the sensor are black. Being that sensor might produce a VR signal, polarity would matter. I switched the wiring around and still nothing.

Now being that the wiring is a bit of a hack on this car, does anybody know if the signal from that sensor goes DIRECTLY to the cluster or does it pass through the ECU or similar first. I want to trace continuity back to the sensor as I don't believe the signal is getting to the actual place it needs to go.

If somebody knows the above and it checks out, I'll pull the sensor and verify its a good replacement and that the teeth on the bottom aren't too beaten up, which I've seen is a known problem.

Thanks!

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OK....so after picking up the 1992 wiring diagram traced back all the wiring.

Also, for anybody reading this in the future, the sensor for the actual gauge cluster is on the passenger side of the trans near the back under the shifter area.

The Blue/red stripe wire has continuity all the way to the cluster, the red wire has continuity to ground and the yellow wire has 12v with the ignition ON. This is leading me to believe its a logic board in the cluster issue OR the sensor itself is bad.

I pulled the sensor and it was a little difficult to turn, I don't know if that is normal or not??? The teeth where fine though....

The cluster I changed with came out of an automatic, do those not work in manual cars? (it came out of a 1994 as my car is a 92).

Any input at all would be greatly appreciated.

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Ok, so I replaced the Speed Sensor (3 wire under shifter) with a BRAND NEW OEM Piece from the dealership and the speedo is still fricken dead. What a waste of $200! I've tried moving the needle with my finger while moving because some people have had an issue with the motor losing lubrication (or something like that) over the years.

I'm out of things to check now....wiring from the sensor is good all the way from the trans to the cluster. I've changed the motor out from a known good cluster as well. Any other input would be greatly appreciated at this point.

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