OK, so I bought one of those "bubble taillight kits" so I could get all four lights to work as brake lights. (big Mistake-they'e junk) Anyway, I had them on for a while and they all worked propery. I decided to get rid of the bubble lights because I thought they looked cheap and tacky. I bought four original style taillights and put them on. Now for the life of me, I cannot get them to work properly. When I put my foot on the brake, they all light up, however the right side is very bright and the left side is very dull. When the headlamps are on, the right brake lamps work, but the left side turns off completely. Now, I think it might be a problem with the bulbs themselves, as I'm certain the wiring is correct. ( I have not touched the wiring since replacing the bubble style. Should all four bulbs be the same? (i'm wondering because there are two different bulbs being used) and if so, which is the correct bulb to use? Let me know if I'm in the right direction, or what else I can try. By the way, when I bought the bubble kit, it came with bulbs different than the 1157's that were in the outer lights (I'm not sure of the number) Also, 1157's dont fit in the sockets the bubble kit came with. Should I just replace the inner sockets with 1157's? Any help would be appreciated. If anyone can help me, it's you guys

 

Its the ground, probably on the left side.

 

I was working on my 77 this weekend and only had 4 volts at the socket. I cleaned and reinstalled the ground and the voltage went to 12 like it should be.

 

Ground Ground Ground my 75 replaced the bumpers then had no tail lights and the flasher just came on Cleaned all the grounds all is fine .

 

Yep, it was a ground problem on the left hand side, just as you guys said it would be!! I knew I could count on you guys Thanks again!!