When I first start my 75 Vett, all is normal. When the car heats up to running temperature and I stop at a light, the tach reads high (approximately 2000 RPMs) but the car is ideling normally. If I take my foot off the brake, the tach reads the correct RPM. I believe it to be an electrical problem (possibly a ground floating) but cannot find anything wrong. Any suggestions would be appreciated.
Check and see where the power feed comes from. I'll bet they hooked power to the tach off of the "hot" line to the brake lights. Cure it by running power directly from the positive on the battery or to an open port on the fuse block.
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