Problem with tail lights and related wiring

[tyrantfour]

The car im working on is a late 80s saab 900 with 2.0 auto

the problem is when you press the brake light, all the parking lights get dim to the point where they are barely noticeable. all of the lights work normally until the brake is applied.

my first thought would be excessive resistance. so i go into the trunk and the rear lights are on a "circuit board" so my problem is, what the heck is up with this circuit board? does anyone have any experience with this kind of light dimming or with any info on the circuit board as far as what i should look for.

im used to fords and they dont use this kinda thing...its kinda scary being in someone else water

[Mordac85]

Actually, all of the other lights dimming is not from excessive resistance but decreased voltage, most likely from a decreased resistance elsewhere in the circuit. My Chevy Venture has a "circuit board" which turns out to be just a way to mount the plastic bulb sockets. My son's Saab isn't here right now or I'd check, but I would recommend disconnecting the brake lights one at a time and see if the dimming goes away. You may have a short in one of the boards or harnesses leading to the brake lights that's causing a drop in the available voltage to the other lights. I got some water in the Venture and it caused a lot of funky problems with the lights until I replaced the gasket.