Pwr. Window Switch Problem '94 G20

Hi! On my '94 G20 Conversion van, the passenger side power window opens fine, but won't close. It can only be closed again if two people do it, each "manning" a switch; one on the right & one on the left side. We then have to take turns pushing the "up" switch. With each push, the window raises a tiny fraction of an inch only. It also helps if a third party holds the glass between his hands, forcing it upward. Somone, somewhere, once told me he thought it had to do with a defective relay. If this is true, I'm still at a loss, as neither Haynes nor Chilton address this problem, nor do they even show any relays in the window system on their schematics. Any ideas? Thanks! Bob