Differential Speedo Pulse Generator

[Victor_PR]

Well I finally was able to get under my car and replace the differential pulse generator (PG), which makes the speedometer work. Mine had an intermittent behavior so I bought a new one. In the removal process I noticed that there was a thin wire wrapped around the white plastic part of the PG and fixed to one of the screws that holds the metal bracket that keeps the PG from falling off.

I installed the new PG but did not use the thin wire thinking that the wire was just additional security to prevent the PG from falling off. I ran the car and the speedometer did not work at all. So my question is: could it be that this thin wire is supposed to do something more that just avoiding the PG from falling off?
If it is, could any thin wire work? (the old one is gone)

Thanks in advance for the help. ;)

[chance]

My speedo hasnt worked since I bought the car. I replaced the cluster with a junkyard one and it still doesnt work. I recently changed the sensor like you and it still doesnt work. I suspect that my problem might be a bad cluster or SI board..?

[V8E30]

i believe it is a ground wire to prevent from other signal messing with the signal wave it is producing

[TobyB]

I believe it is an anti- tamper device as required by used car law in the US in the '80's.

Otherwise, you could just unplug the thing and rack up 250k miles then sell it on to a
less successful lawyer as 'hardly used'. Thus completing the yuppie scum cycle.

It's certainly not a ground.

t

[nando]

My speedo hasnt worked since I bought the car. I replaced the cluster with a junkyard one and it still doesnt work. I recently changed the sensor like you and it still doesnt work. I suspect that my problem might be a bad cluster or SI board..?

the SI board doesn't control the speedo. It doesn't ground like the gas gauge or coolant gauge so if the speedo isn't totally fried it's probably not the cluster.

there are only two wires to the diff sensor and there is no shielding. there's a good chance the wires are broken or corroded - you can buy a pigtail with new pins and splice it on. mine had issues because of the wires.

[Victor_PR]

I believe it is an anti- tamper device as required by used car law in the US in the '80's.

Otherwise, you could just unplug the thing and rack up 250k miles then sell it on to a
less successful lawyer as 'hardly used'. Thus completing the yuppie scum cycle.

It's certainly not a ground.

t

This makes perfect sense.

As an update, my speedometer started working this morning on my way to work. After traveling about 15 miles or so, it started working. I'll have to get under my car again and check the 2 wires for damage or corrosion.

Thanks for the replys!:D

[chance]

the SI board doesn't control the speedo. It doesn't ground like the gas gauge or coolant gauge so if the speedo isn't totally fried it's probably not the cluster.

there are only two wires to the diff sensor and there is no shielding. there's a good chance the wires are broken or corroded - you can buy a pigtail with new pins and splice it on. mine had issues because of the wires.

Hmm that makes sense.

The tach is the only thing on my cluster that works 100%. The speedo and temp gauges are dead and the gas gauge isn't right. When it reads half tank the car really is running on fumes.

Where can you buy the pigtail? That sounds like a simple repair