The Monsoon unit can indeed work normally, even though it takes out the battery. The battery drain happens over several hours, so you're not dealing with a dead short (which would blow the fuse, in any event). A surprisingly small current draw can waste a battery, given enough time. An overhead light, left on overnight, can zap a battery in less than optimal condition.
Q: How did the dealer determine the Monsoon to be at fault, vs. the battery itself, or some component of the charging system? VW's in my experience are notorious for poor electrical connections, including those on the battery.
Here is what I would do:
- Try leaving the radio disconnected for a while. If the battery then holds a charge, you may have the problem located. Be aware that the Monsoon normally draws some power for it's seecurity features. In the case of some other electrical system problem (see above), removing this small drain may simply make the problem *appear* to go away.
- Before replacing the radio, replace the dealer. Tell the new guy that your battery goes dead - nothing else. His job is to figure out why you went to the trouble to come in, instead of being out telling people how great VW's are.
- If the problem is definitely the radio and the dealer won't consider making it right - even after you tell him how many friends and family members (potential customers) have heard your story - you can:
3a. Get a new radio. The best deal can be found Anywhere But The Dealer. Ebay is an option, subject to the usual caveats. You don't want someone else's battery drainer. OR...
3b. Consider cleaning the unit yourself. This entails removing the cover (it has to fit back together exactly or the radio won't go into the console again), spraying ONLY a cleaner made for the purpose on any obvious deposit of gunk, letting it dry thoroughly, and reassembling. Be sure to put everything back exactly as it was, even if it's 'only' a foil-covered piece of cardboard. Missing shields means static instead of music. As long as you don't touch anything inside and don't have any parts left over, the worst that can happen is the problem remains. In that event, return to step 3a.
Just make sure other possibilities have been ruled out. Small battery drains are second only to intermittents in terms of the frustration they can cause during troubleshooting.
Good hunting.