>>> HEADLIGHT BULB QUESTIONS ???

[MIDNIGHT RIDER]

I was just in the shop, testing a whole bunch of sealed-beam H6054 bulbs that I got last week at a swap-meet; WAGNERs, Sylvanias, GEs, and Phillips brands.

What I found to be curious is that, with my little analog meter, any combination of two of the three terminal prongs would show continuity.

This defies everything electrical that I know.

It seemed to matter not which terminal I chose for GROUND, I could always get both BRIGHT and DIM by touching HOT to either of the remaining terminals.

This was true on every one of the many bulbs that I tested.


Prior to this, my understanding was that one prong should be shared GROUND (and thinking about this, I may have just answered my own question) and the BRIGHT and DIM elements should be electrically independent of each other; therefore, I should be able to determine which terminal is GROUND by it being the only one that would show continuity between either of the other two; and, when I put the test-leads to the BRIGHT and DIM terminals, I should not have continuity.

But, I guess the reason I can show continuity regardless of which two of the three I test is on account of the shared GROUND, right ??




Now, looking at the back-side of a bulb, laying face-down on the bench, with the center terminal located away from you at "12-O'Clock", the LEFT-hand terminal is 9-O'Clock and the RIGHT-hand terminal is 3-O'Clock; which of the three is GROUND ??

Which is BRIGHT ?? DIM ??


Thanks.

 

[93cc7.3]

12 o clock should be ground i belive and i belive 9 is high beam

 

[NJKen]

Both filaments share the same ground. So, if you test between the high beam and low beam pin with a ohmmeter you will see continuity. The electrical flow will be: High beam pin to ground pin to low beam pin. If there where 4 pins and the ground side wasnt tied together things would be different.
Enjoy
Ken

 

[Agnem]

Same with tail light bulbs. You can get some really funky things going on if you loose a ground somewhere.

 

[Fozz]

Same with tail light bulbs. You can get some really funky things going on if you loose a ground somewhere.

Yep that's true. Kinda off topic, but that's why if you tow and have trailer lighting issues, or issues with the truck when the trailer is hooked up, the tail lights are one of the first places to check. Can also cause your brake controller to act up and your hazards (when on) to apply the trailer brakes through the brake controller. Not to mention it can keep your torque converter from locking up too.

 

[MIDNIGHT RIDER]

Same with tail light bulbs. You can get some really funky things going on if you loose a ground somewhere.

Yep that's true. Kinda off topic, but that's why if you tow and have trailer lighting issues, or issues with the truck when the trailer is hooked up, the tail lights are one of the first places to check. Can also cause your brake controller to act up and your hazards (when on) to apply the trailer brakes through the brake controller. Not to mention it can keep your torque converter from locking up too.

I have had dual-element tail-light bulbs "shoot" and weld the elements together in such a way that weird things as described would begin happening.