Passenger side headlights are dim I installed a.

Tiny
DAN VO
  • MEMBER
  • 2000 GMC SONOMA
  • 145,000 MILES
Passenger side headlights are dim I installed a new bulb with no difference.

Could this be a ground problem? I beleive it had been wrecked in that area before I bought it
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Wednesday, November 21st, 2012 AT 2:03 AM

5 Replies

Tiny
CARADIODOC
  • EXPERT
Yup. To verify a bad ground, remove the other bulb on the left side. If the dim one on the right side goes out, you'll find voltage on the ground wire at the socket. It's supposed to have 0 volts.
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Wednesday, November 21st, 2012 AT 2:12 AM
Tiny
DAN VO
  • MEMBER
Both bulbs on passenger side are dim I had just changed one of the bulbs and it made no difference the bulbs on drvers side are bright. Does each side have its own ground or are they grounded together? Where do theh ground at. If they ground together I guess I might have a break in the wire from one headlight to the other if grounded as one.
Thank you for answering me
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Wednesday, November 21st, 2012 AT 12:25 PM
Tiny
CARADIODOC
  • EXPERT
They normally have a ground on each side but GM has a very bizarre way of wiring their daytime head lights. I'm doing this from memory for all other cars.

When there's a break in the ground wire on the right side, current wants to go through the low beam filament but can't find a complete path to ground. It finds an alternate path by doubling back through the high beam filament, then over to the high beam filament on the left side, then through its ground wire. That's why I told you to remove the left bulb. That will remove that alternate ground path and the dim right bulb will go out.

You can troubleshoot the problem either way. With the left bulb removed, you will find 12 volts on all three wires wires on the right side. With the left bulb installed, you'll only have 12 volts on the low beam feed wire, (or just the high beam wire if that's what's turned on). The high beam and ground wires will have around 6 - 9 volts. If you can't tell which wire is the ground wire, remove the right bulb, then measure the three voltages. One wire will have 12 volts when the low beams are turned on. One will have 12 volts with the high beams turned on. The last one is the ground wire.
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Wednesday, November 21st, 2012 AT 7:31 PM
Tiny
BREANNA STILTNER
  • MEMBER
Where are the headlight grounds located? Having this problem with my 1999 Jimmy.
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Sunday, July 3rd, 2016 AT 6:20 AM
Tiny
CARADIODOC
  • EXPERT
Please start a new question. Once my first reply was posted, this question went "off the list" and no one could see it except those of us in the conversation. That means none of the other experts are going to see your question or have the chance to reply. That does you a disservice because I don't know the answer other than I would follow the wiring harnesses to see if they lead to a ground.

When you type your question, be sure to include the symptoms or the reason you're looking for multiple grounds. Include details like what you've done already, and be sure to list the engine size and mileage.
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Sunday, July 3rd, 2016 AT 9:16 PM

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