StraightTimeStirrups

I have an MSD 8956 RPM Activated RPM Switch I am trying to install and I have having an issue with it.

I have an Autometer Tach that is wired to the ICM Wire for its signal to operate the tach. If I install my window switch connecting it to this wire the car will start, miss, pop and backfire for a couple of seconds before stalling. If I disconnect it the window switch from this wire all works fine leaving all other connections together.

I called MSD and they want me to connect the White Wire from they box to the Negative side of the coil. Which of the 4 wires do I tap into on my 93 Trans Am?

Thanks

StraightTimeStirrups

http://shbox.com/1/93_ign_system_schematic.jpg

I found this on the SHBOX site but I am not sure what is considered the Negative side of the coil.

Joe

StraightTimeStirrups

After further discussions with MSD they told me that the White Wire and White w/Black Tracer are on the Negative side of the Coil. They told me I could tap into either wire with the White Wire from the MSD 8956 so I tapped into the White wire off of the Coil Harness and everything worked perfectly!

I guess that you shouldnt tap into the wire coming off the ICM that gives the tach signal to the Tachometer as it caused me major issues!

Joe