When i turn the headlights on my rear left side brake light seems to stay on like the brake is being pressed but the other brake light is working correctly. I figure its probably the socket but im not sure.

 

Could be inside the bulb itself. Sometimes the filament breaks off and sticks to the other one.

 

Could be a ground somewhere too! I know this isn't the exact same thing but when the ground for my rear defogger came loose everytime I hit the brake pedal, the little rear defogger light on the instrument panel would come one and then go off after I let off the brake!!

 

Its not the bulb. well i dont think so at least. I replaced them all. all the other sockets look real clean but in this one the Dielectric grease has all dried up and there is some corrosion in it. i cleaned most of the corrosion of but still didnt work.

 

Check the ground to the bulb with the brake light filament in it that glows when the running lights are turned on - it's probably open.

Tim