2001 ranger 4x4 issue

hi,
trying to help my neighbor. she is borrowing me her truck to use to get firewood. it's a 2001 ranger 5 spd. she told me that sometimes 4x4 will work and sometimes it won't. i experienced this problem yesterday. i flipped the switchand nothing happens. the day before that i used it and it worked great. but today i hit the switch and nothing, the indicator light didn't even come on. i rolled it forwards and backwards, foot on clutch and foot off clutch. then about an hour later i had to move it......thought i'd try it again. clicked indicator light came on to 4X4 low and it worked.


any ideas???
thank you, Jon