Is there anyway to test a tach. Both of my cars have tachs that dont work. They go crazy when you crank it up and then just read wide open. My 85 Z28 runs off an MSD box and the 86 Iroc is stock.

 

Anybody ???

 

swap in a tach that is known to be good from a camaro/firebird that has the same number of cylinders. See if it produces the same results.

 

Only problem is I can get one that works !!

 

I took a resistance measurement across the contacts for +12V and ground, was varying in the megaohms. Measured resistance across where the signal comes in to ground and was infinite, also infinite from signal to +12V. Got the same results for a V6 tach and V8 tach.

Tests were taken with the Tachs disconnected from the gauge panel. I'm having a V8 tach that isn't working, but its completely dead, just took these measurements earlier today even though i'm betting my problem was bad contact where all the gauges connect. So, if you take an ohmmeter and don't get similar results, you may suspect the tach. Still, i would try to find another tach.

 

Thanks, that was what I was looking for. Ill check the resistance on mine.