On a 95, the signal wire from he power transisor to the gauge looks like one straight run, with a wire branching off to the ecu for the ecu tach signal. I would assume if the harness was bad, except at the harness/back of panel connector, you would have bad engine running. I'd hit the pullapart and see if I could find a used tach. No LC filter in this setup like the 12v motor...

Not responsible for advice not taken...