E30. Electrical checks on electric antenna. How?

["Neil Deshpande" <Ndeshp@xxxxxxxxxxxx>]

While trying to set up a new radio into my car I've had some difficulty =
getting the elec. antenna to actuate.  There is a white wire near the =
radio head unit, but it does not seem to actuate the antenna when =
connected to the radio trigger wire.

I, therefore, removed the trim around the antenna and found the following:

1. The antenna has three wire going in/coming out of the casing.
2. One wire goes to ground.  Obvious since it is bolted to the car body.
3. Another wire is 12V.  Measured between the connector just outside the =
casing and ground.
4. The third wire carries no voltage or current.  I suspect the third of =
being the trigger signal receiver that actuates the antenna in some way.

What I would like to do is feed the appropriate signal to this third wire =
to make the antenna go up and down independently of any radio trigger.  =
The signal probably closes a relay inside the casing.  I expect to have to =
feed the signal across this third wire and ground.  If I don't get any =
responses, I'm going to start at 0.5 V and start going up!

Does anyone know what I should apply to it?  Am I even right in thinking =
it is the trigger wire?

Thanks.

Neil Deshpande
1988 325 is
1989 325 iC

P.S.  I read about how easily everyone else does their radio install and =
wonder whether I'm missing something really obvious or is it that the car =
has just been too badly hacked up.

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