I have a 2002 Subaru Outback. The rear right brake light housing cracked, and filled up with water, shorting the bulbs. I thought I was clever in taking the light unit off, draining the water, changing the bulbs, and caulking the crack with silicon. This worked for a while, then the battery died. I couldn’t really figure out why - it was a year old, and had no prior issues starting the car. I swapped out the battery for a brand new one, and that seemed to solve the issue for a week. Then the car refused to start all over again. I remembered the brake light, checked it - filled again. So I replaced the unit and the pig electric line, and charge the battery. This seemed to solve the problem, but then the car failed to start after about 3 weeks.
One additional detail is the dial light switch on the driving shaft. One is able to turn this to adjust light settings. Regardless of position, the lights turn off when I turn off the car. However, failure to start seems to be additionally related to the position of this switch; if it’s switched all the way back towards the driver the car appears to start consistently for weeks on end, BUT the tail lights fail to turn on in this position (though the brake lights work). Alternatively, dialing the switch all the way away from the driver turns on the tail lights, but seems to be related to battery drain.
I’ve checked the health of the battery and the contacts - everything checks out. At this point I’m wondering if it’s an electrical fault or the alternator.
If anyone has any input, I’d love to hear your thoughts.