fuel gauge and speedo

Is it a workhorse chassis? they had a recall on actia instrument cluster.

Sounds like a ground problem. Try running a temp ground wire to the dash and someplace on the vehicle frame. If that solves the problem, install a #10 or #12 wire from the frame to the chassis of the dash for a more permanent look.

Or it might be the voltage regulator for the dash instruments. I had that go out on my 75 Ford, it was a easy fix. My buddy said look at the gauges. Turn on the emergency flashers. IF you start to see the gauges fluctuate with the emergency flashers (fuel goes up and down with the lights coming on and off) then the instrument panel voltage regulator is bad.

Do your running lights work? If you have a short in the running lights, then they will not work - the spedo might not work as well. Change the fuse for the running lights. That might bring it back on? That happened with my 97 Bounder based on a Ford F-53 chassis.

When I was towing my brother's trailer, there was only 9 volts at the rear bumper when the running lights where on, so plug in his trailer with 20 additional lights, and it went over 20 amps, tripping the fuse. I was able to hook up a relay (like a fog lamp relay rated at max 30 amps) so that the 9 volts turns on that new relay, and then I applied up to 20 amps to the trailer light plug from a separate circuit that had already been installed from by coach battery to the water pump (and was nearby, with #12 wire going to it). That solved the amperage and voltage problem, the trailer lights where pretty bright too!

I need to change my running lights on the Bounder from incandescent to LED someday. Yes I already have had the LED bulbs for 3 years now. . .

Good luck!

Fred.