Rear Window Wiper Washer Motor problems of the 2006 Chrysler Pt Cruiser

Last winter the rear windshield wiper quit working completely. Now the front windshield wipers will not work on high and when they are turned on high, they just stop in the middle of the windshield. Sometimes when I turn them off they will go all the way down and then about 1/4 of the way back up and just stop. I am concerned that I will not be able to see out the back window and that the front wipers will completely stop when I am driving. I will not be able to see and it will risk other drivers and people during hard rain or snow. I have read many complaints about this and some cannot even drive the vehicles. I have checked the fuses, replaced the blades, made sure there is washer fluid and had a mechanic tell me that he has had complaints of the same thing. When the motors are replaced, the wipers still do not work.