candidate for a window relay ???
 

Just finished installing my windows. New regulators. new motor. pass Window goes up and down good with the used rubber installed. Installed used rubber on drivers side and about 3/4 of the way up it struggles and stops short by 1/2 inch.( I can push it with the motor help and it will go up. Is there any adjustment ibn the way it rolls up in the channels? Will a relay help me? Thinking rubber is the issue and going to reinstall. Without rubber window goes up and down perfectly. Anyone had success in trimming the rubber? Not a show truck just a daily driver. not sure on adding relays.. Also going to see if I can slide the regulator a little one way or another as there was some body work done around the four regulator holes.

Re: candidate for a window relay ???
 

Can you remove the door panel, and back-probe the motor connector to watch for voltage drop during operation?

Alternately, find another motor connector, and run large wires(12 gauge?) straight to the battery for a temporary test. Bypass any switches and connectors enroute. If this experiment significantly changes performance, then yes, a relay should help.