Hi

I tried my new NOS 15982 window switch and the rpm readings seem wrong, or at least fluctuating in a very bad way.

At idle the rpm is the same as on the Autometer gauge but with increasing rpm the window switch reads about double the value of the Autometer. Now and then it falls down to correct rpm but seconds after it doubles again.

Everything connected as outlined in the manual and the other functions are working ok. I suspect a bad/distorted/wrong tach signal, but it is connected to the same wire as the Autometer gauge.

I have the tach wire connected to the white wire going to the coil.
There is a white wire going between the coil and distributor also. Is this a better place to tap into?
Or are there any places where I can get a better signal for the window switch? At the ECU?

The car is a 1988 Camaro 350 TPI/HSR, stock ignition.

BR
Jan