Having searched around a bit I haven't found out quite wha I'm after so here goes:
I have a 1991 RS that had a carbed 350 swapped in by the previous owner. Lately my speedometer has only been working when its warm out, or after I drive for a while so I figured that there's a loose connection of some sort. Being a 91 I assumed that it was an electric speedometer but I've seen several posts on the board here implying that it is impossible to have the electric speedo without an ECM and I'm pretty sure that was removed when the engine was swapped for a carbed one. Looking under the car I found a plug coming from the back of the 700r4 transmission which I assume is a speed sensor of some sort and I didn't see anything that looked like a speedometer cable. Also one wire (green insulation) is simply flapping in the wind and I'm not sure which wires are which to begin with. Does anyone have a wiring diagram for this? Also, what else should I be looking for in the process of solving the problem? I'm assuming the hanging wire isn't doing much since the speedometer does work at times. Perhaps being green its a ground?

 

Anyone?
If this is something obvious that I somehow missed in my searching at least tell me that and I'll go search more.

 

I think they don't like answering questions about speedo's around here

I haven't got any replys to my autometer speedo question yet either

https://www.thirdgen.org/forums/elec...-problems.html

Sounds like we are having smiliar problems.

 

The ECMs didnt drive the speedo's in the RS's. There is a buffer box under the dash that split the signal from the VSS and sent it to the ECM and the speedo.

 

So at least it is possible. Thank you for the reply, I'll try to track that down now that I know what I'm looking for.

 

any luck my car is having the same problem and its annoying

 

Dig you guys ever try pushing against the instrument cluster when the speedometer is not working and see if that fixes it while you push it in a certain place?

A common problem with the later clusters is that the connectors on the back can lose connectivity when they aren't positioned exactly right. You can take off the cluster and bend the prongs up to make them contact better, and you can adjust the torque of the 4 bolts holding it in place.

Since it works when it is warm out or after warming up, it is likely just a loose connection somewhere... metal expands when it gets warmer. I had a similar problem with a broken turn signal switch, would only work when it was really hot. So if those connections are fine, I would dig around and just look for loose wires. But start with my first suggestion as it is by far the easiest to fix.

 

I was thinking the same thing about a loose connection although I haven't found it yet. I didn't know the connections on the back were known for being bad so thank you. I'll try the wires on the back as soon as I can tear it apart. However, how I can't press on the gauge as there's the clear plastic plate in front of it. I am still a little bothered by the cut green wire though.