Our daughter is driving a 1990 Subaru Loyale push button 4-wheel drive with around 200,000 miles.  It has served her well since we bought it in 2011.  The green 4-wheel drive light in the center of the dash is not lighting up consistently when we press the 4-wheel drive button.  I believe it is engaging but not so sure all the time.  Any suggestions for solving this?  Thanks.