420A RPM problem/aftermarket tach

[adio_67]

Okay i have a 96 talon nt and i have an aftermarket tach and i hooked it up to pin 73 white wire on the ecu and my rpms read only half of what they should, ive searched and searched i cant find the answers please any help will be appreciated, and i know the big tach are pointless in NTs but i like them thanks again.

 

[luv2rallye]

Do you have the tach set for 4 cyl? Also is it the kind that uses 5v max pulse (not 12v)?

 

[adio_67]

yeah its set for 4cyl and it says connect to 12v source so idk? its really bumming me out.

 

[luv2rallye]

Well there is one lead on the tach that goes to +12v. Do you have a good connection to ground on the ground lead? Are you sure you're not firing on just 2 cylinders? I suppose you could try temporarily connecting it first to ECU pin 3 and then pin 11 (coils primaries) just to see if it works but for sure you'd read half then. Or maybe you have a bad ECU for the tach signal.