Hey out there,
Have a 1988 Cutlass Supreme Classic with the rally instrument cluster. The speedometer - odometer broke as the 80 K original mile car sat since 2006.
My buddy had a Speedometer Gauge from a 1979 and it works HOWEVER, on mine
what is the black plastic looks like plug in (but it isn't) with 2 wires that hook with a very small screw near the speedometer housing on
the backside of the cluster??? We can't figure out what that is. On his 1979 it has the indention where one would go but no screw hole
and the indention is solid not hollowed out.
Thanks for anyone's time.

 

The CCC cars (electronic Qjet) used a Vehicle Speed Sensor that mounted to the back of the speedometer. An optical encoder in the speedo provided the signal. The 1979 cars didn't use CCC and didn't need the VSS.

 

Thanks for your reply. I took the car up the road and the speedometer seemed to work and the odometer turned as well.
Is it a big deal to hook it up?? Kind of confused. Thanks Cory

 

I'm afraid I'm confused by your description and questions. Is your car a 1988 or a 1979? Is the speedo you are trying to use a 1988 or a 1979? Does the car have the computer controls on the engine or not?

The VSS is used by the CCC computer and by the cruise control on the later cars. If you have these items, you need the VSS for proper function. If not then you don't need it.

 

Yes computerized. It's a 88 but the speedometer cluster I put in for a 79 seems to work okay.

 

Well, I'm surprised you don't get an error without a VSS signal.

 

Yeah me too, the speedometer seems to be fairly accurate and the odometer is turning well. It's as much as I could hope for.