At my 33 series 3 the fuse and relay for the electric windows is located somewhere behind the steering wheel, under the dash. I had exactly the same problem some time ago. But it was a bad connection somewhere. I suggest you spray all the conections with WD40 or something similar. In my case, only the drivers side window stoped working. If you have the owner's manual, there is a pic there with the location of the relay and fuse.
I have a problem with my 33 Series III Electric Windows. It appears strange to me that Only one Relay is used for 2 doors. The Passenger's side Window Only opens from the Driver's Switch, the Passenger's Switch doesn't work. It illuminates and shows a little current in the motor but wont move the window. Checked all the connections, replaced some and made them new but its not the problem ! Can Anyone help ?!