Low beam headlights work intermittently

Tiny
MCFLOYD910
  • MEMBER
  • 2007 BUICK LUCERNE
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 140,000 MILES
Replaced bulbs, and checked fuses. Can't find reason for low beams to stop working. First it was the passenger side. Then it started working, and now the driver's side has quit working.
Saturday, January 25th, 2020 AT 5:56 AM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,709 POSTS
I just went through the wiring schematic for the headlamps. Nothing makes sense as to why one would work and not the other. The switch sends one signal (one wire) to distribute the power. Both sides and both beams have a common ground, so if one side stopped, it would be both high and low beam. The switch sends one signal to the body control module, when then powers the low beam / high beam relays. In turn, the relay distributes power to the bulbs.
Now the relays are not typical relays. They are PCB relays. Basically, that means they are part of a printed circuit board and are not serviceable. I attached several pics below of the system. The first one is the PCB relay. Next, I attached the entire system. Take a look through it to see what I am referring to. In all honesty, the first thing I would be checking in this situation would be the sockets themselves to see if they are damaged, overheated, corroded, or anything that could cause such an issue. Also, if the light isn't working, take a test light or volt meter and confirm there is no power to the socket.

______________________

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

https://www.2carpros.com/articles/how-to-use-a-voltmeter

https://www.2carpros.com/articles/how-to-check-wiring

____________________

Let me know what you find. I hope something here helps. Now, if both low beam stopped, that could be a totally different situation, so let me know.

Take care,
Joe
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Saturday, January 25th, 2020 AT 8:22 PM

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