Tach Wiring Questions

[bdeliman]

What drives the pulse that comes out the green tach wire behind the air conditioner? What drives the bar dash tach gauge, and how are they related
to the RPM value that gets displayed in the ECM via a scan tool? I understand that the dash tach is unreliable. I had a VDO tach modified to work in the GN. The dash guage and the VDO guage display the same value, significantly higher than the output from the scan tool and the actual RPM of the engine.

 

[FastRegalWE2]

ttt for ya

 

[Turbo Brian]

The wire that sends a signal to the dash tach is a white wire that comes out of the ignition module and goes into the pass compartment through the body connecter. Try to tie into that wire and check for results.