The left rear window on my '99 Suburban stopped working. It's an old truck so I replaced the window motor. Worked great when done......and then didn't work an hour later. Step 2, I replaced the rear door switch. No change. This was relatively cheap guessing. Now I'm to the driver's door switch, which is more expensive to replace. Before I do that, how do I trouble shoot correctly? I have power and ground at the rear door switch. I have continuity through the switch pins when tested with an ohm meter. Where does the door ground to the body? In the B pillar between the doors? I ask because I could have ground when testing with a volt meter but it may not be good enough to carry a load.