Voltage backfeed to led bulb
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Laughing Gas
Joined: Jul 2007
Posts: 753
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From: Phoenix
Voltage backfeed to led bulb
Since I have rewired my 61, a weird issue has come up. I am using a blue led bulb for the high beam indicator and when the headlights are on in low beam mode there is a 4.5 volt back feed to the indicator light causing it to glow. The bleed is coming from the headlight bulbs, I am running H4 bulbs and have tried switching the bulbs to a different set with the same results and this includes using sealed beams too. So my question is can I use a resistor to defeat the low voltage bleed while allowing 12V to get through when the High beams are on?
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Joined: Jan 2001
Posts: 57,017
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From: Virginia
I am suspicious you might have a grounding problem at the bulb itself. Unplug one bulb at a time and see if it's a problem with both bulbs or just one. Unplugging the bulbs with the headlights on low beams makes the problem go away correct?
Once you figure out if it's both bulbs or just one, I would find the common wire on the bulb, pull the connector out a little bit or some how be able to hook a temp scrap piece of wire to the common terminal and then run the other end of the wire over to the battery negative and see if that makes the problem go away.
All the power for the low beams should go out to each bulb, and then go to the common ground on each bulb back to the neg of the battery. If there is some resistance in the ground circuit, some of the voltage will find a easier path backwards through the high beam side of the bulbs and backwards up into the dash and light the highbeam indicator.
Once you figure out if it's both bulbs or just one, I would find the common wire on the bulb, pull the connector out a little bit or some how be able to hook a temp scrap piece of wire to the common terminal and then run the other end of the wire over to the battery negative and see if that makes the problem go away.
All the power for the low beams should go out to each bulb, and then go to the common ground on each bulb back to the neg of the battery. If there is some resistance in the ground circuit, some of the voltage will find a easier path backwards through the high beam side of the bulbs and backwards up into the dash and light the highbeam indicator.
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