Troubleshooting Speed Sensor

[f4tj0n]

I'm looking for some guidance with troubleshooting my speedo issue.

I've recently had my cluster repaired and did a differential swap from a worn out 3.25 to a freshly rebuilt/upgraded 3.25. During the diff swap process, I had to replace the speed sensor connector because I forgot to unplug it and destroyed the original one.

The problem is that the speedometer is not registering speed properly in my car, but is confirmed working in other vehicles. At highway speed, the speedo sometimes works, but most of the time doesn't. The odometer is still registering mileage, but no where near what it should be (registered 20 miles and have driven maybe 200-300).

For troubleshooting, I've checked continuity from the connector at the differential to the connector at the cluster and that checked out. Also, cluster confirmed working in other vehicle. Is there any testing I can actually do with the speed sensor itself without swapping it?

[f4tj0n]

According to the wiring diagram, the speedsensor in the diff is basically a switch that opens and closes when the sensor wheel goes through it. Does that mean I can test continuity on the two poles in the sensor while spinning the wheels by hand?

[roguetoaster]

You can probably use an audio or visual continuity confirmation, but the reading may be out of range on a MM, but that's not based on direct E30 diff sensor experience unfortunately.

If you broke the sensor before did you also replace the plug? Have you checked your splice if you replaced the plug and did it that way? Have you tried hitting the dash when the speedo drops out in case you have a damaged circuit up there?

[twright]

According to the wiring diagram, the speedsensor in the diff is basically a switch that opens and closes when the sensor wheel goes through it. Does that mean I can test continuity on the two poles in the sensor while spinning the wheels by hand?

I don't know if you can see the signal change when you spin it by hand.

I do know you can see the signal change with a voltmeter if you drive it. I doesn't change much, but its enough to see it at idle in 1st gear. When you stop, the signal will go back to where it started.