I have an interesting (or so I think) question about my '90 740 Instrument cluster.

My odometer only works if the car has been running approx 50 miles in a row...almost invariably it only works like that. I get the feeling it has something to do with "SOMETHING" warming up inside the cluster/behind the steering wheel. During this past HOT NYC summer, sometimes the odometer would start working right off the bat even and run for about 100 miles or so (essentially, I felt until something cools down).

Recently, I've noticed my fuel gauge acting very flaky...it always seems to be off by a FRACTION. For example, if i shut off the car when the tank is showing as half empty, and then I start the car a few minutes later, the tank will show as a few ticks off from half-tank. once the car is running, it will SLOWLY recover the difference, but it's a troubling thing.

I recently went to a junkyard and got a used instrument cluster that I figured I would replace my current semi-working cluster with. This is my first car, so I know very little about cars, but I am an engineer by profession, so I trust that I can make some common sense infrences. I noticed how the mechanic took out the cluster from the junk car, and I had a few ideas (and maybe you guys can tell me if I'm wrong)

The instrument cluster is basically just connected with wires to the rest of the car. So, if my current cluster works in this random fashion (and when it does,
it works just fine, without skipping any numbers or getting stuck anywhere),
could it be the cables that are bad?

Could be there be a disconnect somewhere in the cables that is causing the hiccups with the odometer? I know everyone says that it might one of those bad cogs that causes that problem - but the odometer DOES work at times.

If this is the case then shouldn't I be looking to get those cables replaced? Are those even replacable? Because even changing the cluster isn't going to solve anything then?

About the fuel gauge? I noticed the problem only after my car came back from servicing from a volvo dealer. Could they have screwed up something? I wonder if the circuitry has gone bad (soldering etc), but again, I wonder if it's the wiring?


Any help would be appreciated. I've been holding off changing the cluster because of this nagging issue?