Ok i just bough a new monster tach w/shift lite, and i hooked it all up but when the engine is running the rpm's are almost twice as low as the stock tach that is still hooked up.all i did was splice into the old tach so both can still work. But i dont know why the rpm's are so much lower and i know u cant calaberate the tach because it says u dont need to touch anything if it is a v8.
Sry for it being kinda lengthy just trying to get the most details for ya. Thnx

 

you can check it with a timing light that has a tach built into it....also does it sound like it's idling at the speed that the monster tach says it is? factory gauges can be off......also does it have good power and ground wires.....these can screw up the readings as well.

 

thanx for the reply. Ya i checked all of it and i went back to where i biught it and returned it and got another one. Still is doing the same thing i checked all the wire but i dont know exactly where the green wire goes. It is a 85 z-28 tpi. If someone can show me a pic of where the green wires that would be awsome. Yah as u can c i am a real moron when it comes to wireing .

 

O yah, u can definately tell it is way off cause at like 2500 on the autogauge it is like at almost redline or a little less on my original tach and u can hear it screaming so i know it is way off.

 

is there a mode switch that might allow you to use it to read really low rpm more acurately?