The TACH on both of my Jeeps are the same kind.
My connections are as follows (your may be different, see your diagram):
BlACK----is CHASSIS GROUND
REDis Connected to "ON" when the Key is ON--"OFF" when the key is OFF
WHITE----Connected to my dash lights, Tach illumination will dim with dash lights dimming (using my light control)
GREEN----Connects to NEG COIL!---Insure you are not on POS COIL!
The other thing you must do is INSURE the SELECTOR SWITCH is on (4 CYCLE) 8 CYLINDERS
Other than that, maybe there is something special with Newer Vehicles.I do not know your rig well.I know Older "REAL" Jeeps well!
Let me know if this helped at all. Maybe someone else will pop in and aid you.
On "Mr. Jeep"--12 O'clock on steering wheel--Air fuel beside it. Top Right on "WILLY" in the cluster of 6-2" gauges (oil pres and Temp are most important and closest to me, on both vehicles)
Images (Click to make bigger)
Monday, December 27th, 2010 AT 2:31 AM