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brake light troubleshooting

jboomer

Sr. Member
Joined
Oct 17, 2007
Messages
506
Loc.
Havelock, NC
I just replaced my tail light harness and the "light sockets" for the tail light/brake lights with new ones. The issue is, something's not right! Here's what I'm seeing now that they're installed:

With just the brake pedal depressed, I get the left bulb bright and right bulb dim.

With only the headlights on, I get the left bulb dim and the right bulb bright.

With the brake pedal depressed and the headlights on, I get both sides bright.

With the brake pedal depressed and the headlights on and the left blinker on, I get the correct blinker going.

With the above listed and the right blinker on, there's no flash and they are both bright.

My head is hurting trying to figure out what is wrong where. The harness was plug and play...no splicing or nothing. The light sockets had to have the original "connector" spliced into them so they would plug into the harness. However, that shouldn't be the problem since the two wires that go into the socket that touch the bulb are only hot individually unless both the brakes are mashed and the headlights are on. Clear as mud?
 

bronko69er

EB Addict
Joined
Oct 16, 2006
Messages
4,599
Loc.
Renton, WA
Yeah, Im thinking thats right, if the brighter filament is in contact with the running light lead and the dimmer filament is connected to the brake/turn signal lead, you would get those symptoms.
 
OP
OP
jboomer

jboomer

Sr. Member
Joined
Oct 17, 2007
Messages
506
Loc.
Havelock, NC
My assumption was that the leads couldn't be reversed in that each lead only supplies power to one filament (2 filaments in the bulb). If you apply the brakes, only one lead is supplying power to one filament. If you turn on the headlights, then the other lead supplies power, hence the other filament is activated and the light appears brighter.

I guess maybe I was wrong. So if that's the case, naturally it's the right side that needs the wires switched?
 

bronko69er

EB Addict
Joined
Oct 16, 2006
Messages
4,599
Loc.
Renton, WA
If you look closely at your 1157 bulb, you will see that the 2 filaments are different, one is a smaller and shorter (the brighter one) and one is longer and thicker (the dimmer one). The pegs on the side of the bulb casing make is so you can only insert it one way and prevent the issue you are having now.
 
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