I bought a 2002 Jetta for my daughter and it was working fine last summer whan she was driving it every day. I have been trying to drive it once a week but left it unattended for approx 6 weeks before Easter. She had no problem starting it over Easter weekend, but on Sunday, the battery was dead. My mechanic could not find a drain on the battery, the battery was 18 months old so he trickle charged it and it was OK. I then left it for a week and the battery was dead again. I trickle charged it for 10 hours and it was OK. Today my mechanic found a 41 Milliamp drain, which he says is normal. He replaced the battery under warranty. Could there be anything else going on here? Like a short that's draining the battery?
The paracitic load on the Jetta shouldn't be over 15 ma. 42 is too much as it is almost 1/2 amp. The best way to check the draw is to start with the alternator by disconnecting wires one at a time and see if it drops.
The amp meter should be in series with the negative battery lead on the amp scale. If you don't have a digital voltmeter you canb get a good one for a bout $15.00
The VW alternators are famous for having a small drain problem. If it is good pull one fuse at a time and see when th current drops, When you isolate the circuit let me know. Good luck