nozzleman0358

I have a 1990 LX 5.0, i have msd ignition box, wires and coil on it. i got a autometer 5" tach from a friend. i installed the tach and double checked the directions. The tach is working now that its installed but its reading about 500 rpm lower than the factory tach is. anyone know what the problem might be ?? and yes i hooked the tach to the msd box and not the coil.

PRO50SC

Mine does the same thing.

rust_stang

Umm probably because your aftermarket tach is correct, and your factory tach is a POS.

WhiteWindsor

Factory tachs are known to be off expecially after 15-20 years. Mine only reads about 200 rpm difference.

nozzleman0358

ok so sounds like my factory tach is the one thats off. thanks for the input.