sounds like the rheostat in the switch is dying. mine does the same thing, its just not bad enough yet for me to move up my list...
1985 CJ7 Project
Phase One :
5.3L Vortec/4L60E, Moser axles for AMC20, Twin Stick'd Dana300 - Completed
Bedliner, Rollcage, Seats, BESRK Rear Bumper w/ tire swing, Soft Top, and a few other goodies - Mostly Complete
Waggy 44 front, Scout D44 Rear, 4.56's, ARB's (F/R) SOA with YJ Springs, 35x12.50x15 BFG MT - Not Even Close to beginning
Also a mostly rust-free 1970 Scout 800A That I'll get to start working on someday...
Chrome won't get you home...BUT Rattle Can Black may just get you back"