i got a tailight problem on my 80 gmc sierra grande?

[John]

the drivers side tailight works when lights are on and when i turn blinker on but when i step on brakes it doesnt light up i lookeed at the wires everything seems to be in order what could be the problem
i also bought a new bulb

 

[knuckleheaf27]

i'd check to make sure you have the right bulb.