Windows are fused in pairs ie, right front and left rear and left front and right rear. If both of the rears are working and when you trey to actuate the front switches nad get no indication of current draw, then it's gotta be the power feed to the front window switches. I would pull them and check the sockets with a test light or volt meter. If you get no 12 volt source, then it's got to be wiring or soemthing either in the feed relay or the fuses. There aren't too many other choices. The probability of both motors failing at the same time is rather low, although the connectors in the doors could be at fault, but that will be a better proposition if the switch sockets show 12 volts with the test equipment. Good luck.
2000 Dodge Grand Caravan SE
No matter what you fix, there will always be something else to fix..
"Warranty" is just another way of postponing the inevitable.