The Stovebolt Site Forums The Shop Area The Electrical Bay Help with brake light trouble shooting

1949 Chevy 3600

Hello all, I need some help

I'm trouble shooting the LR tail light. I have running lights in the back but no brake or turn signal.

How do the dual element 6V bulbs work? Is there a resistor in the tail light?

Here's what I know:

-Flashers in the front work
-Flasher on the RR works
-RR brake light works
-Both bulbs work normally in the RR housing
-Both tail lights work
-The LR brake light and turn signal do not work

The wiring to the light must be okay because the tail light works.

Any ideas?

Thanks Y'all
J&K

Check the grounding of the LR light socket. It's possible for the tail light circuit to find a ground by backing up through the brake light wire until brake or turn signal voltage is applied to that wire- - - -then everything goes dark. It's not uncommon for the socket to lose its ground due to a loose or rusty attachment to the bed.
Jerry

Will do Jerry.

Does that mean that both wires on the tail light will have voltage and the ground is the chasis?

One wire is hot for the tail light, the other serves as the brake light and/or the turn signal. It's possible that the bulb is the problem- - - -the ground for both filaments is soldered to the brass base, and if that ground gets broken, the same problem will happen as a bad ground on the socket. Change the bulb first- - - -it might solve the problem. The ground between the bulb socket and the bulb base is the most common reason for the problem you're having, which happens VERY often. If the mounting surface for the tail light assembly is rusty, or somebody has painted everything before it was assembled, run a ground wire from the socket assembly to the frame with clean, tight connections everywhere.
Jerry

Got it!

Had power and ground. Everything was as it should be according to my multimeter. I scratched my head for a while retracing my tests and everything checked out. Until I grabbed my test light. Although I could see the voltage with the meter there wasn't enough amperage to light the filament. After that I found a butt connector on the firewall that had poor connection due to corrosion.

Wow what a doozy!

Thanks for the help Jerry

You need to check battery connections

And you need to read the whole thread before offering advice- - - -he fixed it!
Jerry