OK, I'm assuming you have installed a new battery (should be step one). I'm also assuming you removed all fuses, cleaned the fuse ends and the fuse terminals. (do that with batt disconnected). Also it would be a good idea to remove and clean the major chassis grounds. (batt, chassis, engine, etc....)
Seems like when folks have really weird electrical problems, the alternator can cause odd things to happen. The brush assy can be replaced.
This is at least a starting point, and the more knowledgeable folks can chime in.

__________________
Jimmy L.
'05 Acura TL 6MT
2001 ML430 My Spare

Gone:
'95 E300 188K "Batmobile" Texas Unfriendly Black
'85 300TD 235K "The Wagon" Texas Friendly White
'80 240D 154K "China" Scar engine installed
'81 300TD 240K "Smash"
'80 240D 230K "The Squash"
'81 240D 293K"Scar" Rear ended harder than Elton John