Headlights go out with fog lights on

Your car has high intensity discharge headlights, since you have fog lights. The HID bulbs probably need to be replaced since they are intermittently producing light.

Try leaving the fog lights off and see how long the headlights continue to produce light. IMO the fog lights primarily serve a cosmetic purpose; they do not improve the driver's ability to actually see the driving terrain.

 

The so called fog lights mainly serve to make the car be seen by others.

 

If the ballasts or HID bulbs aren't defective, then I'd be worried that the small current draw the foglights place on the electrical system is causing a problem. The car should have much more capacity than that to handle electrical demands.

Perhaps the 12v auxiliary battery is getting weak and nearing it's time for replacement?

SCH-I535

 

In the 05 you can't turn the fog lights on without first having the HIDs on. Perhaps there is an aftermarket switch that has been installed incorrectly?

 

Did the car come with the extended warranty? Patrick is correct, your bulbs are going out and need replacement, with an extended you might luck out, there was a tsb about the bulbs, shouldn't be hard to find, might not apply, well worth looking for.

 

It is more likely that the HID bulb is bad, than the ballast. I suggest that you replace the bulb on one side, and see what happens.

Unless your car was in a front-end accident, I doubt that there is a problem with the wiring harness.

 

I agree with Patrick that the HID bulbs are likely the problem.
There is it seems a difference in the operation of the fogs in the US compared with Europe. Here the fogs can be operated with just the side lights " no need for headlamps" as having the headlamps on with the fogs would defeat the purpose of fog lamps. Reflected light from the headlamps from the fog reducing vision that the fogs are positioned to avoid.

John (Britprius)

 

The bulbs with the brightest, effective downroad illumination is in the 5k to 4.3K color temp. 6k and higher is just for looks.

 

Congratulations on your success. Before you declare victory though, I suggest you leave the headlights on for an extended period at night to make sure they turn on, and stay on.

 

In the US it is generally unlawful for fog lights to be turned on, independent of the headlights.

 

In the UK fogs can only be used in poor visibility conditions, fog, falling snow, or heavy rain and spray. Not doubting you for one moment, but seems strange that the design of a flat beam of light close to the road to get under the fog, and light the road should have to be only be used with headlamps blinding the driver with reflected glare from the fog.

John (Britprius)

 

This is probably why, in the US, fog lights primarily serve a cosmetic purpose. When the fog lights on my 2004 are turned on, I can barely see a slight increase in the light pattern at the bottom of my viewing range.

In the US, if the vehicle is in motion and if there is a need to turn any lights on (after sunset, in rainy conditions, etc.) then the headlights must be on. You cannot legally drive the car with only parking lights on for example.

There is no restriction regarding when fog lights are on, which results in some drivers leaving them on all the time, which irritates and blinds oncoming traffic...