Pedro
I recently fitted HID's, and sucessfully drilled the shunt to cancel the bulb failure.
You have to be very careful when drilling the hole.
The power for the dipped beam travels through the shunt from pin 2-3. There is a known resistance between these pins (0.01 ohms if i remember correctly) giving rise to a voltage drop (Remember V=I*R) between the pins proportional to the current drawn.
The standard 50W bulbs draw approx. 4A each (8-9A) giving a voltage drop in the region of <0.1V. The central control unit monitors this voltage to determine if the bulbs are working.
At 35W, the HID's draw approx 3A each giving a voltage drop of about 0.06v (This is all very approximate saturday night maths before anyone starts).
By drilling the shunt in the location described (see link in my other thread
here, and external site
here), you reduce the cross section area of the shunt, increasing it's resistance, giving a higher voltage drop for your lower current, tricking the central control unit.
If you drill a slightly too big hole (>2mm) or in slightly the wrong place, you will increase the resistance to the point where the remaining shunt heats up and burns out, breaking the supply to your headlights.
FYI: From the research I did into this it turns out standard fit HID's use pins 1-3 on the shunt. The wiring in the fuse-box is different to accomodate this.
NOTE: If you re-fit higher power bulbs, you will need a new shunt after drilling it, as the higher power bulbs will burn out your drilled shunt.
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