Re: Nova tail light problem
Dual filament bulbs are bayonet based with indexing nubs to make the bulb install one-way only. I found on a friend's car where someone had "forced" the bulb in...the wrong way, which resulted in just what you are experiencing.
Start with the bulb, make sure it is not damaged or have conductive debris between the two bottom terminals and examine the inside of the bulb socket for corrosion, trash, etc.
I have also experienced that not all aftermaket bulbs are equal, some of the cheaper brands don't mate very well with some sockets.
1969 RS/SS Vert
1031 Engineering llc