The following VFAQ was created to help people replace their malfunctioning power antenna mast. As always remember the lovely legal disclaimer that I do not accept any liability for yours or anyoneâ€™s actions who may follow any of my guides.
So your antenna is sticking going up and down or refuses to move yet the motor and clutch work just fine, well you've came to the right place. Why spend $100+ on a new antenna when you can have a brand new mast for it for a mere fraction of that?! But just to make sure that this is necessary, did you perform a good cleaning with the Hirschmann antenna cleaner? You can find this on eBay from time to time for only ~$3ea.
This is a very easy thing to replace, especially if you can find a helper to turn the antenna off and on. The only problem which could be encountered is if the old one was way over tightened just like mine was. I ended up making a tool which held the bottom in place while I turned the top free. Simply remember righty-tighty, lefty-loosy and it makes the job much easier to do while the antenna is up rather than if it is down. Just turn the piece until it screws out of the portion on the car such as pictured below.
After this is out turn the radio off or set the antenna switch to off, wait for it to come down a little ways then turn it back on to send it up. Grab a hold of it on the way up as about the same time it normally makes it its max height it'll be in your hand, free of the car. Notice the way the plastic tooth drive is, the smooth side is pointing toward the rear of the car and the geared side is pointing toward the front.
Reinstall the new antenna's plastic drive the same way, after you know it is properly in the gear's grasp have your helper turn the radio back off again, it pretty much guides itself in but watch it just to be sure. The motor will shut off just a little high so you can tighten the nut again I only went finger tight this time though, if you have a problem later you can always tighten it a little more. After turning the antenna on and off one more time it will be just like new. As a confidence booster I will let you know that I made this months after changing the mast on my car, it was so simple that I took it apart and redid it just for the pictures, furthermore I installed it without a helper twice.
A DIY for replacing the Hirschmann antenna gear can be found HERE.
Discuss this DIY here.