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Paul Bennett · 04-11-2020, 07:52 AM

I put a 12v 7" sealed beam bulb on a clean workbench with a 12v battery and voltmeter. Connect battery -12v to the ground terminal of the bulb per diagram above and +12v to the hi beam terminal. The lamp lights and +12v comes out of the low beam terminal enuf juice to light another bulb.

Nothing to do with grounds or old wiring. I'm interested in knowing why when I apply voltage to either hi or low beam terminals, voltage appears at the other terminal.
If I apply voltage to a 6v bulb NO VOLTAGE appears at the other terminal.

Guys, if a chicken died in the back seat of an '35 Ford at 25mph, someone would claim it had a bad ground. Please concentrate on the 12v bulb if you have ever messed with one. (and forget ground)

Thanks 41F1 for the nice socket diagram.

04-11-2020, 07:52 AM	#7
Paul Bennett Senior Member Join Date: Sep 2016 Posts: 628	Re: 12v Headlight problem I put a 12v 7" sealed beam bulb on a clean workbench with a 12v battery and voltmeter. Connect battery -12v to the ground terminal of the bulb per diagram above and +12v to the hi beam terminal. The lamp lights and +12v comes out of the low beam terminal enuf juice to light another bulb. Nothing to do with grounds or old wiring. I'm interested in knowing why when I apply voltage to either hi or low beam terminals, voltage appears at the other terminal. If I apply voltage to a 6v bulb NO VOLTAGE appears at the other terminal. Guys, if a chicken died in the back seat of an '35 Ford at 25mph, someone would claim it had a bad ground. Please concentrate on the 12v bulb if you have ever messed with one. (and forget ground) Thanks 41F1 for the nice socket diagram.