All I can tell you is that in my case the bad module was the window that didn't work. I guess one way to test M.B. Doc's theory that "the rear module can effect the front module" is to unplug the rear module/motor. If the front still fails then I would suspect the front. The module is built into the motor, which is integral (although removable) from the regulator assembly. I got the whole thing from a junk yard for 60.00. And they guaranteed that it would work. And it does.

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra