Looking at the schematic from a 88 shop manual, (which appears to be the same as the 89, wiring colors are the same) It looks like the rear window switch and motor are connected to the same harness by a common ground. I am going to disconnect the switch on the rear door and check that. by the way, the motor in the rear passenger door is dead as far as I know. I am wondering if it might have a constant electrical load on it causing my problems. Don't know what else to trouble shoot other than the relay, which seems to be fine, because the drivers side front and rear work fine. I haven't figured out if there might be a relay for each side yet.