I’ve got an issue with my 2k Jetta. I’m driving along, and all of a sudden the dome light comes on, and it starts dinging like I’ve left the key in the ignition. If I unlock the doors, or open and slam the drivers door, it calms down. Any ideas?
It sounds like the door closed switch is not functioning as designed. I don’t know how it is set up, but I would find it and do some checking and cleaning of contacts.
Bad microswitches in the door lock mechanism are a known issue on the 99-1/2 - 2005 Jettas.
VWVortex has a ton of information on this. One member wrote a DIY guide to fixing it.
You are not the only one with electrical issues on a VW. They are awesome cars, but fall short when it comes to locks, lights, wiring, etc… Small price to pay, I say, but good luck fixing that!