Intermittent instrument cluster malfunction
After months of losing my dash instruments intermittently, it became permanent. I called the Freightliner rep and he did a valiant job of helping me work through the problem. We tested the dash warning light bar computer console by pushing the computer toggle switch to the right and holding for 5 seconds. This activates a diagnostic menu. It showed none of my instruments were receiving a computer signal from the dash computer. I bought a new warning light bar/dash computer - expensive. Bad news - the instruments worked, but not consistently. The idiot lights all work, the odometer works, but instruments only on and off. Then I had an idea. I disconnected the wiring harness from the output side of the warning light bar/dash computer, removed one of the daisy chain wires that connects one instrument to the next, and reconnected this new wire so that it went from the computer to the tachometer. Viola - it worked the tach. Did the same to the fuel gauge - it worked. It turns out the wiring harness that ran from the computer to the instruments had a short. I replaced the harness and so far so good.
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