I have a 99 2.5l manual 2wd ranger xlt. I ave the "phantom wiper" issue in that the wipers will just suddenly turn on. I think I have narrowed that down to the Multifunction switch. (which I am going to order). But also when my a/c, headlights, or wipers are on in any combination my voltmeter goes down like something is pulling alot of power. I have seen it go to about 1/4 up from the bottom of the gauge. I am wondering where I should start looking. I checked my a/c and it has the right pressure. But then again when the a/c runs sometimes when at idle the gauge will go down. Any ideas before I go insane and start doing surgery? Thanks

 

sounds like an alternator starting to fail.