Yeah - I sorted that out yesterday and found a surprise. All the way to the right on the row of lights at the bottom of the cluster is an "OD Off" light -- I can read/see it by shining a light on the outside of the cluster. I thought that light would be illuminated with 12V+ to the yellow wire. However, when I hooked a 9V battery up to the yellow wire in question, I was surprised to see a nice little green light that just says "OD" more in the middle of the cluster. That one you can't read from outside the dash - it has to be backlit; all these years I actually thought that space/light in the cluster was un-used.

I presume that one or the other of those lights was on at all times when the car was running and both on for test with ignition on?

Anyway - left the yellow wire loose and marked --- may find a use for that one just to signal me that some yet unidentified device is powered. Perhaps have it light up when the cooling fans come on for the a-c or when a-c clutch energizes. Or maybe have it light when the cruise control is energized. I marked temp gauge, oil press. idiot light, tach feed, oil pressure gauge, oil temp gauge and alt. light (alt exciter) wires when pulling the 5.0L out. I removed the blue OD power feed all the way back to the fuse box - #11 I think.

I also left the large gauge white/black stripe wire that fed power from the fuse box to the heat/a-c fan in place -- it comes off #3 25A circuit --- it'll be perfect to feed power to the new HVAC system which is fused with a 20A circuit. That will power the fan, the heater control valve and all the air diverter functions.
--
82 242 6.2L coming...; '10 Cayman S; '15 Honda Fit