Windows

I'm looking for advice on the following rather weird problem on my '89 280 GEL.
When purchased as a project, the electric window on the drivers front was inop. I knew the door was being changed for a solid one anyway so I wasnt too concerned and did no investigation apart from fuses...which were fine. The interior lamp was noticed to be dimming when the switch was pressed, no noise evident from the door area.
I have today fitted the new door which is all electric like its predecessor (although the central locking appears to be retro which i will be resolving in due course), the window being down ( i presume to aid handling as so were the other three from the same car. I fitted my loom into the new door (as factory, no scotchloks or chop n joins), and still the bloody window won't work (i havent swapped motors around or anything, its as it came). The only investigation i've had time to do has been a test lamp on the two wires which come down to the motor, which both show live when the button is pressed in the appropriate direction, yet still i have no noise from the motor. I even tried a direct fly lead live from the fusebox. Nada, nothing at all.....
Is it just a coincidence, ie 2xknackered motors, or can anyone think of anything I havent done/checked? As there are only 2 (live) wires to the motor, how does it earth, by attachment?
All suggestions gratefully received - I hope it doesnt rain in the next couple of days.......