Running light problem

[Ken333]

When I’ve got my running lights/ headlights ON one bulb on the passenger side turn signal is lighting both of the lights inside the bulb instead of just one. Any idea what’s causing this?

 

[Erik the Awful]

Either the filament broke and fell over onto the other filament, or you have a two-filament bulb jammed in a single filament socket, you have two wires shorting, or the two filaments share a ground that is broken off and it's backfeeding and finding a ground somewhere else.

 

[Ken333]

Either the filament broke and fell over onto the other filament, or you have a two-filament bulb jammed in a single filament socket, you have two wires shorting, or the two filaments share a ground that is broken off and it's backfeeding and finding a ground somewhere else.

I found out that the bulb had gotten moisture into it and it was shorting out, I got a new bulb and seal and it fixed the issue. I’m glad it wasn’t any wiring problem though.

 

[Erik the Awful]

When I was a tech I had a customer bring in an Altima, saying the cruise control didn't work. I test drove it and the cruise control worked just fine. I pulled it into the shop and one of the other techs told me, "Every time you hit the brakes the parking lights come on." The customer had changed his own brake light bulb and jammed an 1156 single-element bulb in place of an 1157 dual-element. The single nub on the bottom of the bulb was large enough to bridge the terminals, so when he turned on his headlights, it backfed to the cruise control circuit, and when he hit the brakes it backfed the parking lamps.

The lead tech then taught me about how 1157s are bad about one filament breaking and laying over onto the other. It's not common, but back when 1157s were the most common bulb, you were bound to see a few.