Two problems related to horn assembly have been reported for the 1999 Volkswagen Passat. The most recently reported issues are listed below.
I had smelled hot electrical components for about a week pryor to loosing my lights, horn, turn signals, tail lights, heater fan, and wipers. It ended up being the ignsion switch once repaced the surge of electricity caused a short under my dash.
I had shut off my car and when I went to turn it back on I had no lights, turn signals, dome light, horn, climat control or radio. I took it to the dealer they told me it happens on beetles and golfs all the time and that it was the ignision switch. They showed me the switch when they pulled it out. It had gotten so hot it melted right through the wires. There is no safety recall on this but if it gets hot enough to melt metal it could start the car on fire.