I had a Porsche 914 D-Jet that behaved badly in wet weather. It had me stumped for longer than I care to think about. Eventually I noticed where someone had pierced the insulation on the wiring in various places trying to troubleshoot some malady. I put silicon sealer on every spot I could find. I never found all of them. Sometimes when I turned on the wipers the headlights would raise and lower, out of sync mind you! It looked really odd.

If your harness has been pierced, you may have a difficult time finding the holes. Depending on the diameter of the tool used to pierce the insulation you may or may not find the breaks in the insulation. A 20 gauge needle -- maybe. Anything smaller than that would be very difficult to find.

Hopefully your wires have never been so probed.