Rear Fog Light Warning Icon

Audi A4 B6 and B7 Headlight Switches have the Rear Fog Light Warning LED active, unlike the VW Headlight Switch.

The Audi A4 also has two different style switches - one has an extra "AUTO" position and the other has the "Lowline" three position Headlight Switch as per the Mk IV / 6R Polo.

These switches all still use the Mark IV / 6R Polo style Headlight Switch with the larger body.

However, the internal camshaft that controls the electrical outputs as the Switch is rotated to different positions is completely different and will not work with the .:R32 wiring.

We are still interested in the 'Lowline" Switch however, as you can, in fact, swap the printed circuit board into a VW Headlight switch to obtain the extra Rear Fog Light Warning LED.

I secured a secondhand Audi Switch to obtain the required circuit board.

Naturally, you need to also select the Switch version to match your existing Switch with either Front & Rear Fog Light positions or only the Rear Fog Light position.

Converting Mark IV Headlight Switch

Note: You can use the SEAT Arosa Switch to do this modification if you only have Rear Fog Lights. The Audi Switch seems to be more readily available, however, it appears that all Audi "Lowline" switches only come with provision for Front & Rear Fog Lights!

The Audi A4 B6 version uses all red illumination for the symbols, so this would be the preferred version for a Mark IV Headlight Switch.

The Audi A4 B6 "Lowline" version circuit board should be a direct fit into your Mark IV switch.

By careful observation you will note the retaining lugs to separate the two halves of the Headlight Switch.

Once the tabs are released the Headlight Switch will only pull apart about 10mm. At this point you rotate the front of the switch anti-clockwise 90 degrees. This will disengage the driveshaft from the knob going into the camshaft in the rear half of the switch. Some switches also have a small spring around the drive shaft, so do not lose it as it will be reused.

Fully separate the two halves and remove the circuit board from the rear half of the Switch. You may find that it is quite firm, but it will come off with some careful levering. It may also assist to open the claws slightly with a flat screwdriver blade to release some tension. Some switches, unfortunately, also have the contact bars on the circuit board soldered to the claws coming from the rear of the switch, so they would need to be unsoldered in that case.

Swap the Audi circuit board to the Mark IV switch and reassemble the switch in reverse order.

What you need to end up with is the complete Mark IV switch housing with just the Audi A4 B6 circuit board inserted.

Converting 6R Polo Headlight Switch

The Audi A4 B7 "Lowline" version circuit board is required for the 6R Polo Switch. The B7 version has the separate green "Parking Light" icon as per the Polo 6R version.

After the modification you will note that the "Audi" green LED is a slightly different shade to the "Polo" green LED for the "Parking Light" icon.

Before disassembly, note how the circuit board is sandwiched between both halves of the switch with no gap.

Disassembly is the same as above, however some modification is required to the 6R Polo front half of switch before the Audi circuit board will sit flush inside like the original Polo circuit board.

The Polo uses SMD LEDs and the Audi still uses older style LEDs which project higher off the circuit board.

There are two light diffusers inserted into the Polo face that need to be removed for clearance. They can be removed by cutting away the tiny retaining tabs and pulling the diffuser out with a pair of needle-nose pliers. They just slide out once the retaining tabs are clear.

There are also three lugs (indicated with yellow arrows in photos) that need to be dremelled or cut away to enable the Audi circuit board to sit completely flat.

As you can see the Polo circuit board has cut-outs to align with these three extra lugs which the Audi circuit board does not have:

Once these obstructions are removed you can reassemble the switch.

You will note when you put the Audi circuit board onto the Polo rear section that one of the claws no longer lines up or touches one of the bars on the Audi circuit board. This is OK! This contact serves no purpose in the Polo Headlight Switch!

Reassemble the switch in reverse order, making sure that the circuit board sits flush without any gap as you previously observed.

What you need to end up with is the complete 6R Polo switch housing with just the Audi A4 B7 circuit board inserted.

This is the final result:

I already had the Rear Fog Warning activated in the FIS cluster, so now I have two warnings:

Parts List

Red illumination only for dimmed lighting

6H0 941 531 E 01C      SEAT Arosa Headlight Switch - Front & Rear Fog Lights

6H0 941 531 D 01C      SEAT Arosa Headlight Switch - Rear Fog Light only

8E0 941 531 A 5PR      Audi A4 B6 "Lowline" Headlight Switch - Front & Rear Fog Lights

Red illumination for dimmed lighting with additional green "Parking Light" emblem

8E0 941 531 C 5PR      Audi A4 B7 "Lowline" Headlight Switch - Front & Rear Fog Lights

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