Golf with Rain Problem

This page, and the links below, are an effort to map out the logic of how to deal with a car problem.

Diesel engine, manual transmission

When it rains hard, the car won't start. This is after sitting in the driveway for a few days, an ordinary circumstance.

No power goes to the ignition; the electric locks don't work; no LEDs or illumination on the dash; turning the key gives no clicks or other sounds.

Possiblities (I think these are the only two):

I think (a)(2) is the place to focus: How to determine *where* the moisture is accumulating to complete a circuit, and draining the battery?

It's hard to diagnose this with Dr. Google, because although many people report similar problems, they rarely give a complete description. (E.g., "car won't start" could mean the engine cranks but doesn't catch, etc. etc.) Diagnose Golf Rain Problem

I'll try to build a model on the Federated Wiki of how a car's electrical system functions. I'll be deepening my learning about cars and wiki at the same time, so it might be slow going.

Car Electrical System