2000 Montero Sport - Intermittent changes: headlights dim to bright (with lights on dim or bright), A/C fan speed, temp guage bounces. Good battery, alternator passes all test.

 

check those battery terminal ends, also have the battery load tested.

 

The terminal ends have already been replaced and the battery is new - I did although have it load tested, and proved good.
Still need schematic, as I suspect a grounding issue and NEED to find all
grounding points both under the hood and in passenger compartment... Any
suggestions ???? Rob