Mysterious battery drain

Hi! I own an '03 Passat. A couple weeks ago it sat over the weekend and Monday morning, it wouldn’t start. Took a jump.

Battery is less than 1 year old. Brought it to my foreign mechanic and he did a load test, key off drain test, and multi-meter. All were fine. Although I was pretty sure I hadn’t left anything on, I figured that must be the answer.

Last week, I was gone for 8 days and you guessed it, the car didn’t start when I returned. He ran the multi-meter again. He kept resetting it after it cycled off and it never showed excess drain. He opened each door to see if a switch might be sticking, and nothing. He says I could pull out each fuse and see if I could narrow it down (and that’s a big “if”) but how I can leave my car idle for 3 days at a time and do this times 20, is beyond me. His suggestion was to keep a battery tender hooked up, or a disconnect to switch off the battery when at home.

Curiously, the first episode of this occurred 2 days after I had the back door replaced with a salvage door. It does seem to be closing fine, but do you think something in there could be the culprit?

Is there any hope in solving this mystery? I am going on a 4-day business trip next week and wonder if I will be hitching a ride home from the airport…

“Curiously, the first episode of this occurred 2 days after I had the back door replaced with a salvage door.”

Did you run this by the mechanic? If not, you should. Really raises a red flag in my mind, anyway. The used back door may not be the exact same “application” as your original door, electrical-wise, considering all the options that might have been available on your vehicle.

Do you have access to the old door? You could possibly have your mechanic remove the wire harnesses on the current door, and install the original harnesses, or at least compare the 2 wire harness scenarios first.

How large is the draw (in milliamps) that you are trying to “narrow down”?