Tech Article Title Author Date
Prevent Fog Lights from Cutting Out when Using Brights Christian J. Long 1998

This modification can be used to prevent the fogs from cutting out when using the brights.

Materials:
Auto Inline Fuseholder (Radio Shack Part number 270-1213; $1.99)
15 amp fuse
Wire crimper set

On the Audi A4, if your fog lights are on, they are designed to cut out when you turn on your brights. The light on the fog light switch remains lit when you turn on your brights, but in fact, the fogs do cut out if you will take notice of the headlight unit itself. I have made these instructions to enable you to keep your fog lights on in conjunction with your brights if you should choose so. By replacing a relay with an inline fuseholder, you will bypass the fog light cut out feature, and the fogs will continue to stay lit when you turn on your bights, giving you more light. The fogs will still be unavailable with just your parking lights on, or no lights at all. I make NO claims to this being safer or better for foul weather, this is just a mod I did and decided share with the A4.org community.

DISCLAIMER: There are a wide variety of local laws in place that could make such a modification illegal. Due to overachieving cops and sue-happy lawyers, I must add this disclaimer that it is your responsibility to check with your local laws to verify that such a modification is within local ordinances. It is also dangerous and inconsiderate to other drivers to use your brights in conjunction with your fogs while in traffic, so be sure only to use your brights on isolated roads with no other cars in sight or on off road applications. The design of the A4 fog light being integrated in the headlight unit will most likely keep you from ever encountering any problems with local constables anyway. The fog lights appear to be simply part of the regular headlights, and no one will suspect that you have fog lights in the first place.

The relay which is responsible for cutting out the fog lights when you switch on your brights is located at the #7 relay location (the furthest left location of the middle row of relays on the relay panel under the driver's side dash), see the drawing for a detailed map of the relay location. You can access the relay panel by removing the lower knee bolster or through the fuse box. If you go through the knee bolster, there are four 8mm hex bolts holding the bolster in place; 2 are under the rectangular plastic strips across the top of the knee bolster, one is located in the fuse box, and one is located in the lower right corner of the bolster. When you remove the two rectangular plastic strips to get access to the 2 top hex bolts, pry the strip off with a small flat head screwdriver and be careful not to bend it, as it may crack or split. You can also access the relay through the fuse box. Remove the fuse box cover and above the fuses will be a small window into the relay panel. Going through the fuse box window will be somewhat tricky due to the limited space, you will most likely have to remove the knee bolster instead.

Remove the #7 relay, and check the function of the fog lights to verify you have pulled the correct one. Now take your inline fuseholder and crimp a connection at the end of each wire that matches the size of the relay's connections. Keep the length of the wires on the fuseholder long enough so that you can reach the fuseholder from the fuse panel relay window, about 2 inches. Install a 15-amp fuse in the fuseholder. Install the connections of the fuseholder in the locations previously occupied by the relay connections #87 & #30 (see drawing). Now your fogs should remain lit when you hit your brights.

Reader comment by Michael DiBlasi 

On my 1997 A4 2.8QM, there was no relay in slot #7. The fog light relay was in slot #10 (see Christian's illustration). I followed Christian's article above except removing the #10 relay instead of #7. It seemed to have had the same results. Also, I found it much easier to remove the knee bolster than trying to go through the fuse panel cover. The Knee Bolster is very easy to remove.

ANOTHER DISCLAIMER: All information given in these instructions is no way an Audi approved modification. I claim no responsibility for any problems you may incur or any warranty issues that may come up as a result of this modification.


Fuse schematic
Click picture for enlarged version