My 1990 740 wagon (Regina model) failed state inspection because all 3 brake lights didn't work. My mechanic said there was a break in the main wiring harness and wired around the break to make the lights work (wanted to avoid costly replacement/repair of main wiring harness). Now when I apply the brakes, the "light out" dashboard indicator goes on which he says is because of how it's wired and not to worry. I can live with that.

When I got the car at the shop, the right rear power window was stuck down. The power lock on this door won't work now either. Both worked fine before. Mechanic isolated the window from the control switch, provided independent power, and determined the motor was not working at all; totally shot. He claims there is no way what was done to fix the brake lights could have affected the power window because they're on separate circuits with different wiring harnesses and therefore it's circumstantial. Could this be true or would it be possible to do something inadvertently to affect the right rear door like this?

Any thoughts? Many thanks.