Help! Brake light problem on '86 Transam

[sixpack_sid]

I have an '86 Transam and I'm having a lighting problem. I don't know if this is a coincidence or not, but I changed the alternator a couple days ago and when I hooked the battery back up it sparked. I didn't realize that the pos wire that hooks to alt was touching the alt core & it sparked. When I drove into work someone told me my brake light was out. On further investigation, when I turn on the lights & running lights, they all work. But when I hit the brakes the whole pass side running & brake lights go out. It appears the back up lights come on-but dim. When I have the running lights & lights off, the brake lights work fine. When I opened the lenses up & put new bulbs in & tried them, on pass side both of wires in bulb itself lit when the parking lights were on. When I stepped on the brakes, they all go out on pass side &  both driver & pass back up lights go on. I'm pretty sure it didn't do this before. Any ideas where I should even start looking would be helpful. I'm really stumped.

Thanks!

[Tilar]

The only way that could have done anything is if you happened to pinch some wires when you put the alternator on... But even then I don't see how that would affect your brake and running lights.

[Charger_Fan]

To me, it sounds like a grounding problem in the rear harness. It's lighting up other lights because for whatever reason, that's the easiest path to ground on that car. You need to remove all the plastic covers back there & examine the wire harness...you may even have to remove some of the loom around the wires to see what's going on. Keep in mind that your fuel pump & fuel sender wires will probably be in there too & may be grounded through that same harness.
Not being familiar with that particular car makes me only guess, but I suppose there could be a fusible link set up in the harness back there to ground everything & that may have gotten burned when you grounded the alternator wire.