Opened up the tach assembly this weekend to see about the possibility of changing/modding the tach face. My attempt looked good in the daylight, but the backlight with the headlights on or the indicators looked like an SOB. So I gave up on that until I can figure out a way to cut down on the illuminence through the background portion.

Anyways, while I had it open, I ran across a connector on the back of the tach that I don't know what it does. There is a 7 pin connector that connects the tach to the car... but at the top of the assembly there is a 5 pin connector that isn't connected to anything... anyone know what this does?

I can't find a pic and my digital is out of batteries at the moment, but then again, if you don't know what it does, you don't really need a picture

 

Have I actually stumped the experts?

 

It might be for the boost guages?
PROMINI Instrument Console - Cooper S

 

Maybe it's where the speedo plugs in when you have the NAV system.