Pegging the tach is different then reading high...
reading high often means board has problems w/ bad caps and/or resistors.
peg temp etc gauges means sender section of circuit is open.
but tach and speedo "meter" is driven by a chip. The chip itself or "meter" have problems. Could be loose "meter" connection to anything.
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Dr. Ian Malcolm: Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should.
(Jurassic Park)
The Ogre's Fiero Cave