Hey guys,
I'm new to the G35 community and hoping I can find some help figuring out this issue. I recently got an oil change done on my 2006 coupe. I had noticed earlier that day that one of my fog lights (also daytime running light) was not coming on, so I had them replace that at the same time rather than doing it myself.

Now the fog lights come on whenever the headlights are on, and go off when the headlights are off. I can't control them with the fog light switch anymore, and they also do not come on as daytime running lights anymore. It's almost like they rewired the car so that they are directly connected to the headlights!! I checked back with the garage, and they say that all they did was replace the blub.. Does anybody know how this could have happened by replacing a bulb?? I know the daytime lights worked before and at night I could control them with the fog light switch. Doesn't make any sense to me, so if anybody has any suggestions or has heard of this before, please let me know!

Thanks,

 

There are two main bulbs on our headlights. The "low beam" is a 35W "DR2" Xenon HID bulb and is located in the upper portion of the headlamp. The bulb in the lower portion of the housing is a two-filament halogen "HB2" bulb that does double duty as our "high beam" and fog lamp. The stock bulb is 60/55W. (There is a 3rd standard double-filament incandescent bulb for turn indicator and parking light. That one is 21/5W.) These are all 12V bulbs.

Now... You mention daytime running lights so does that mean you are in Canada? If I read the manual correctly the way this works is "with engine running, lighting switch off or in 1st position and parking brake released" power is supplied to the daytime light control unit which then runs the "high beams" in series - meaning they operate at 1/2 illumination.

All I can offer is an explanation of how I understand the system operates: When you turn the headlights on (not "auto" but 3rd position) the upper HID bulbs should light - they are brilliant white in color and focused with a sharp upper cutoff point. Turning the fog light "ring" switch should add the lower bulb to the mix, still with a focused cutoff. Adding the "high-beams" should add another blast of light from the lower bulb - this one widely focused with no cutoff. The fogs and high-beams will appear slightly yellower in color than the HID low-beams. I believe you can flash the high-beams without having any lights on but the fogs will only run when the low beams are on.

I can't speak from personal experience but I'm quite sure the sockets for these bulbs are NOT interchangeable. There is a ballast for the HID that would not likely agree with the halogen. Easiest possible answer is that your shop put in the wrong kind of halogen bulb which has unbalanced your daylight running circuit and maybe disabled your fogs?

Hope all that helps........

 

Hi,
Yes I am in Canada, I meant to mention that in the first post but it must have slipped my mind. So as far as I can tell, the xenon bulb is the regular low beam, and also acts as the high beam. The lower halogen bulb is for fog and daytime running light (not for high beam). When everything was working fine, my halogen bulbs were on during the day while my xenons were off. Switching the headlights on, turns the xenons on and the halogens off (unless I have the fog light switch turned on).

Good point about the bulb type, they may have put the wrong bulb in which somehow makes contact with a terminal that it is not supposed to. I will take both bulbs out today and have a look to see if they are physically similar or have some obvious difference.
thanks,

 

Sorry if I wasn't clear:

The Xenon bulb (which is nearest the top of the headlamp) is low-beams only. There is only one "filament" in that bulb and so only one output level. It is focused through the optics of the headlamp so that if you point the car at a wall and turn on the low-beams you will see a sharp cutoff at the top - so it doesn't shine in other driver's eyes.

The Halogen bulb (closest to the road in the headlamp) serves THREE purposes in your car. It has two "filaments" and so has different levels of output:
#1 = high beams. Either flashed by pulling the light switch "lever" towards you or added to the low-beams by pushing the lever forward while the lights are on. This is a wide, unfocused light which does shine in other driver's eyes.
#2 = fog lights. Only available when you have the low-beam Xenon bulbs on, and supposed to be controlled by the little ring switch next to the light switch on the lever. This is a focused beam which fills in below the cutoff line of the Xenons - helps you see the curb or the center line.
#3 = Daytime running lights. Your car uses the high-beam element of the halogen bulbs as daytime lights - but it runs them at 1/2 brightness.

So again, I don't know exactly what's happening with your car - simplest answer may be the Halogens don't match and that has screwed something up... But your original description of the problem is confusing. Remember, the fogs are only 1/2 of the Halogens, the high beams are the other 1/2 and THAT 1/2 is supposed to serve as daytime running lights.

Let us know what you find.

 

also... your Xenon low-beams should stay lit whenever you have the lights turned on. Fogs and high beams only add to that.
The only exception to that rule is daytime running lights which use the 1/2 dim halogens only...