Intermittent problems can be a tough nut. If the bulbs and sockets are ok I would suspect a processor in the BCM or IPM based on your getting it to work again with a power cycle. I would try to eliminate the multifunction switch first. The most obvious way is to jiggle it. If it cures or induces the problem try a new switch as stated. The right way is by using a multimeter. At contact three (white with light blue stripe wire) of the switch connector you should get a consistent resistance reading going left or right with the switch. You'd be looking for a major change in that consistent reading.
Looks like we're all answering at the same time. BTW - No flasher module on your van.
Last edited by Cougar41; 12-07-2012 at 03:42 PM.