Volvo 960 light problem

I know there are a few of you who have responded to lighting and specifically lighting problems with Volvos, but mine seems a bit different. Here goes:



The car is a 1993 Volvo 960 Wagon. When you’re driving around in the dark, the tail lights work fine on both sides. When you step on the brake, one of the tail light / stop lights goes out completely. So, one of the lights doubles (it’s a two-filament bulb) and the other one goes dark.



I tried switching the bulbs from one side of the car to the other and, and the problem persisted on the same side of the car. Then I replaced the offending bulb with a new one and it didn’t work out. When I checked out the new bulb, one of the filaments was melted. Now I have two melted bulbs and one good one.



Any ideas?



Thanks!

You have a bad ground to the bulb socket on the side that goes dark.