Audi Convertible aerial issue

[slinky]

Folks, a chap in the office has just picked up an Audi drop top, he sent me this email...
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Just need a bit of guidance probably. I bought John's 1996 Audi Cabriolet, and the electric aerial retracts, but doesn't extend. I have had it out, but not apart. Motor is definitely working on radio switch off, but doesn't sound like its working on the switch on.

I am after some pointers about how they function, as in is there a pulse or voltage to drive up, then a separate pulse to reverse. Any advice really, or a pointer at a good forum. I'm not bothered about getting my hands dirty, but you can waste a lot of time not knowing what to look for. Its not an original stereo, and John has never got round to it, I suspect it may be a mis-connection/no connection. I know the aerial is straight, probably a bit dirty - so that is my next step to strip it down, but as I don't get a motor noise on fire up, I see that being a major issue. Ideally I want to keep the original, rather than replace it.
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Any advice would come in handy..

Cheers all,

slinky
587racing.com