Tachometer reading too fast

[NAPA 68]

I have a SW vintage mechanical tach that I had retrofitted by Classic Insturments. The unit is about 4 1/2 years old. All of a sudden, it is now reading about 1000 RPM higher and reads higher throught the RPM sweep. Nothing has changed and the car still runs fine. Any ideas before I send the unit back to Classic Insturments?

Thanks,
Tim

[marks914]

Sounds like noise in the system. Try switching the dip switches back and forth and then back to normal mode for your setting. Usually that does the trick for a climbing tach.

[kyle @ rfw]

Try double checking the grounds on the engine and the gauge.