Brake lights ground where?

[gdizzle]

Ok let me ask a real stupid question: on my 66 dart, I am thinking about trying the LED option on the back lights.

I noticed something interesting today, I pulled the socket out of the light body (brake) and hit the brakes at it lit up. It is my understanding that these light sockets ground via the light body, so if I remove the socket from the body, how can it still light up? Is it using the 2nd contact in the socket as a ground path somehow???? Please enlighten me. Otherwise I think I may have a bare ground somewhere?
I also noticed that one of the lights was acting weak, but when I inserted it back in the light body, I see a little mini spark and the light is full power now.?

 

[Rustedwrench]

Ok let me ask a real stupid question: on my 66 dart, I am thinking about trying the LED option on the back lights.

I noticed something interesting today, I pulled the socket out of the light body (brake) and hit the brakes at it lit up. It is my understanding that these light sockets ground via the light body, so if I remove the socket from the body, how can it still light up? Is it using the 2nd contact in the socket as a ground path somehow???? Please enlighten me. Otherwise I think I may have a bare ground somewhere?
I also noticed that one of the lights was acting weak, but when I inserted it back in the light body, I see a little mini spark and the light is full power now.?

The power to the brake bulb will take any and all paths to ground. In this case the power will go from the brake bulb power terminal in the socket, through the filament for the brake bulb to the socket housing, then through the tail lamp filament to the adjacent license plate or tail light filament, through that filament and then to ground on that other socket. Kind of like going around the barn to get to the outhouse but it gets there in the end. The more filaments the power goes through the more voltage drops so the un-grounded bulb will be dimmer than normal.

 

[RedFish]

There should be only 2 wires at a rear lamp socket. Brown is park lamp circuit. Green or yellow for left and right are both brake and turn. Yes the brake lamp current could back feed through the park lamp circuit.
It would attempt to power both park lamps and the tag lamp. Maybe not light'em up brightly but at least show power on a meter.
You probably just had a weak ground connection at that other ( dim ) socket.
I don't read a actual fault at this point but for what its worth... Whenever I look at a fault in rear lighting, the 1st thing I look for is where trailer lighting may have been tapped in. I've seen some pitiful hack jobs over the years.

 

[gdizzle]

There should be only 2 wires at a rear lamp socket. Brown is park lamp circuit. Green or yellow for left and right are both brake and turn. Yes the brake lamp current could back feed through the park lamp circuit.
It would attempt to power both park lamps and the tag lamp. Maybe not light'em up brightly but at least show power on a meter.
You probably just had a weak ground connection at that other ( dim ) socket.
I don't read a actual fault at this point but for what its worth... Whenever I look at a fault in rear lighting, the 1st thing I look for is where trailer lighting may have been tapped in. I've seen some pitiful hack jobs over the years.

great guys, this puts my mind at ease. Now if I could only figure why when I plugged the new LED bulbs into the sockets, I get NADA.

 

[RedFish]

LEDs are polarized. Brake lamp current can't backfeed through the park lamp diode. Could you blow them out by applying power without ground ? I don't know enough about them ( never will ).
I think they should be well grounded before power is applied just to be on the safe side.

 

[Yote]

I hope you didn't buy the "cheap" LEDs like I did. Mine lasted from about 1 second on one and 30 seconds for the other. JUNK !!!!
Yote

 

[TrailBeast]

There should be only 2 wires at a rear lamp socket. Brown is park lamp circuit. Green or yellow for left and right are both brake and turn. Yes the brake lamp current could back feed through the park lamp circuit.
It would attempt to power both park lamps and the tag lamp. Maybe not light'em up brightly but at least show power on a meter.
You probably just had a weak ground connection at that other ( dim ) socket.
I don't read a actual fault at this point but for what its worth... Whenever I look at a fault in rear lighting, the 1st thing I look for is where trailer lighting may have been tapped in. I've seen some pitiful hack jobs over the years.

This all sounds normal for the conditions to me also, but I will add one thing.
Whenever I have an electrical issue with lighting I drag out a 20 foot wire and clip it to the battery negative so I can move all around the car supplying what I know is a good ground to all the sockets.
Sometimes it seems like darn near every fault in the electrical system these cars have is a ground fault.