I’m trying to find out why my rear lower tail light goes out when I hit the brakes.With headlights on I am getting 10.25 volts on one of the socket studs and the getting 10.25 volts on both socket studs when brakes are applied, but light bulb goes out.Put in new bulb but same problem. Are there any wise car guys out there that can help with this. Thanks Brian

Headlights on

Headlights on and brakes applied

Socket

 

Make sure the spring loaded contact is actually making contact with the bulb.

 

What year 442 would that be?

 

Its a 67

 

Yeah, I'd agree with oldscutlass. Have a look at that spring loaded contact......make sure it's clean too so give it a little contact cleaner. You're 100% on power to the second contact with the brake on? Double check it with a test light, a multimeter won't load it up.

 

It is most likely a ground issue on the lower housing. With the tail lights on and the brake lights off, that socket is getting ground by back feeding through the brake light filament of the top and bottom bulbs to get ground through the top housing. When the brakes are applied, power is given to the brake light filament and the ground path is removed. With the head lights/ tail lights off, the lower brake light is able to back feed through the tail light filaments. When both filaments get power, there is no ground path to back feed through. If it was the spring loaded contact, the tail lights would not go out. The brake light just would not come on.

 

You can check for a ground issue if you use a small screw driver or pick to scratch/ touch the housing and the socket. With the the tail lights on and someone pressing the brake pedal, you should see the light come on when you ground the socket to the housing. These sockets are notorious for loosing connection to the housing. Corrosion builds up between the housing and socket and the light no longer works.

 

Good call , that’s the next thing I will check out. Thanks for a direction

 

Thanks to ourkid2000 andloaded68w34 After do several tests I determined that the socket wasn’t grounded to the pot metal housing most likely because of corrosion.I didn’t want to pry apart and replace , trying to keep it all original if possible. By drilling and installing s/s screw thru the pot metal and going thru back side of socket I was able make a grounded contact .Thanks guys for the direction