Today took the 87 Quad for a tour of the Apache Trail outside of Phoenix. After getting on the freeway to Globe the alternator started dipping and acting strange. Decided to head back to the barn instead of getting stranded who knows where in the desert. Then I began to notice it only happened above about 3500 rpm (i.e. @70mph). When I slowed down voltmeter started acting normally. I am thinking maybe a slipping belt, but don't know otherwise. Will have it checked this week before the club run up to Jerome, AZ this weekend. Any suggestions? BTW, normally charges at about 13.2v and keeps the battery nicely charged.