I have an electric speedo out of an 88 Firebird that consists of the head and a circuit board. The circuit board has 3 screw tabs on it, suspect for power, ground, and signal. Unfortunately they are not lablelled. I believe I know which one is ground as it goes to a trace that goes all over the board.

I have chased down every source I can think of to try and find a schematic or pictoral that will help identify these. I found on this site and some others a schematic that was supposed to be for an 88 Firebird but it showed some sort of an infrared feed to teh ECU so I suspect it was an earlier cable driven representation.

I am attaching a photo of the board. On the front edge you can see the silver screws in the tabs. The picture clipped the left side of the board but it only goes another 1/2".

Can anyone help me with this?

Tnx Fred in Mesquite, TX

 

You're right, the IR boards were for the cable-driven speedometers.

If you could take a very clear (as in "sharp") picture from the top and from the bottom, that would help us analyze the board. But it would really have to be in high resolution and with good detail (part #'s visible and good lighting).

Was there not a connector for this board with clearly colored wires or anything? That would help with the wire identification.

Lou

 

the speed signal is the left silver tab on in your picture

 

The information is great. I am attaching some additonal pictures that are as close and sharp as I can get. Since they have a little bit of fuzziness I added some text giving IC markings and the like.

I really appreciate your help!

Tnx Fred in Mesquite, TX

 

Well, with hookup it didn't work. 96 GMC 4.3 with 4l60-e going into an 86 RX7

Did some more digging for information and have come up with the following:
1. VSS is working, OBDII program gives a speedo reading.
2. Factory manual shows 4000ppm output to instrument cluster, unfortunately do not have o'scope or logic probe to prove it's good.
3. 88 Firebird speedo has 1001ppm stamped on metal rim around it. No markings on printed circuit board.

Questions?

1. Does 4k ppm signal from vcm get conditioned down to 1k ppm within the instrument cluster or did the GMC speedo's in 96 run at 4k ppm?
2. Will 88 speedo pc board take the 4k ppm input and condition it for the speedo or does it need 1k ppm input?
3. If the 88 speedo needs 1k ppm and the VCM is outputting 4k ppm, will something like Dakota Digital's SGI-5 allow me to correct this?

Any information you can provide is GREAT!

Tnx Fred in Mesquite, TX

 

Anyone?