on my 86 firebird, I went and replaced all the bulbs and bought 2 new tailights cause the others were cracked.

now with the headlights/parking lights off, both brake bulbs on both side come on, but one isnt as bright as the other(all new bulbs) what can cause this?

Also at night when the headlights are on, when I step on the brakes the 2 inside bulbs that only light up when the headlights are on, go off and the brake lights illuminate?

what would do this?

 

Check the wiring to the one that isn't as bright sounds like the wires for the brake light and tail lights are swapped.

 

sounds like a bad ground.

 

thats what im thinking too.

Well me and my wiring diagram got some work to do tomorrow.

 

If you find that your ground wires are intact and you have not corrected your problems, check the placement of your bulbs. It's possible to put your bulbs in backwards. If that is the case, you will get voltage feedback, causing the kind of problems you are describing. This is because the contacts on the bottom of the bulbs do not align correctly with the contacts in the sockets.

 

I found the problem guys The black ground wire that goes to the back cover where the trunk lid contacts the metal plate up there, the wire was unhooked so it never made contact.

Now all the lights work good, as does my brake light on the rear window.