QuestionQUESTION: The headlights on my 2007 Hyundai Sonata keep flickering dim; sometimes they even go completely out for 1 or 2 seconds. Quite scary when night driving. Any suggestions?
ANSWER: As I look at the schematic, there's a host of problems that could be causing this:
1. Faulty low beam head lamp relay
2. Faulty Body Control Module (BCM)
3. Faulty headlamp switch
4. Poor contact at ground G17
5. Any sort of wiring issue causing an open circuit between the headlamp switch and the ground, between the BCM and the headlamp switch, or between the BCM and the head lamp relay.
I'm presuming both headlamps go out.
When they flicker, do they turn off and back on, or do they just dim and return to normal brightness? How frequently do the events occur? Be as specific as you can with each type of event.
When the lamps go out:
1. Try turning the headlamps off and back on to see if this corrects the issue.
2. Do the high beams work?
3. If your vehicle is equipped with fog lamps, when you turn the fog lamps on, does the fog lamp indicator illuminate?
I believe I've seen similar issues caused by faulty BCMs, albeit not in Sonatas.
---------- FOLLOW-UP ----------
QUESTION: Thank you for your response. Here are follow-up answers to your questions: Yes, both headlamps dim and return to normal brightness. Frequency is maybe 3 or 4 times during a 20 minute drive. Yes, the high beams work. I do have fog lamps and the fog lamp indicator does come on. I will check the wire contact this week and see if that helps.
There seems to be some sort of wiring problem because the latest thing that is happening is the air bag light keeps coming on, and when no one is sitting in the front passenger seat, the seat belt light still comes on as though someone is sitting in the seat.
Thanks for your reply.
AnswerIf the fog lamp indicator illuminates even though the low beams dim or go out, this suggests (but does not conclusively prove) there isn't a problem with the power side of the circuit, since the power from the low beam headlamp relay also powers the fog lamp relay coil.
I have seen one vehicle where the headlamps would dim (but not go out) periodicially, which didn't have sufficient engine ground capacity. It was resloved by running a couple heavy gauge wires from the engine to the attachment point between the negative battery cable and the body of the car.
If you car has less than 60,000 miles, I'd suggest taking this issue to the dealer and letting them sort it out. If it has more than that and you're looking to resolve the issue yourself, I'd recommend registering for a free account at www.hmaservice.com. There, among other things, you'll be able to view the wiring diagrams for the vehicle in the ETM (electrical troubleshooting manual) section.
I strongly suspect the air bag issue is completely separate from the headlamp issue. The circuits have little to do with each other, and I've seen a more than a few cars that needed passenger seat cushions due to problems with the occupant classification system.
