Hi - I've just swapped a motorized aerial from one E30 to another. It worked fine on the first one, but wont do anything on the 2nd. However, I don't know exactly which wire is the one that controls the aerial. All the wires into the stereo are correct, all works as expected, apart from no aerial. When I wired it up, there was one (grey and red, I think) wire left over, I tested it with a multimeter to find the was no current coming from it, and then used it as the aerial wire. No joy.
Can I connect the aerial directly to the battery to check it still goes up and down ? I'm guessing that they have a pos. and neg. power leads, then one more that make or breaks the circuit depending on signal from the head unit ?