91 740 Wagon Speedometer needle bouncing all over

[gbl]

I had a problem where speedometer and odometer simply stopped working. Brought it to mechanic, he replaced speedometer sensor, still no good, he replaced instrument cluster...this fixed my broken gas gauge which had been broken for years, odometer works now but speedometer is extremely flaky. Sometimes it works, other times it bounces all over the place, 70mph to 90 mph, 0, bounce up to 30 ...doesn't seem to have any relationship to actual speed and sometimes it does 'seem' to work...mostly it does not. Can anyone point me to a possible fix? Do you replace the entire instrument panel, can you replace JUST the speedometer? I'm moderately mechanical if I can just find a good diagram and instructions. Could this be just a loose cable on the back or the cluster? Any help would be greatly appreciated.

[billofdurham]

Welcome to Matthew's Volvo Site.

Check the connectors on the speedo transmitter in the differential. Whilst your mechanic has replaced the transmitter, a part that rarely breaks down, he may not have checked the connectors for corrosion or oxidisation. They have probbably sat there undisturbed since the car was built and had goodness knows what thrown over them. If in doubt replace the connectors.

Also check the earth (ground) wires for the instrument panel behind the dash and in the right footwell.

Bill.

[gbl]

Thanks, I'll take a look at those, is there a source or instructions somewhere for how you actually remove the instrument cluster if I have to replace it? I've searched the web but I seem to find every model BUT the 91 740 wagon. I can't find where the screws are that hold the plastic cover on the cluster which from what I've read will just pull out once you have the plastic cover out of the way. All I see is just sealed up dashboard.

[billofdurham]

There is a cover in each of the bottom left and right sides of the cluster. Gently pry them out with a very fine screwdriver to expose the retaining screws.

Bill.