HIDs with relay
01-13-2006, 08:06 PM
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HIDs with relay
I installed HIDs in my '94 S4 and they are awesome. After reading up on things I decided to add in a relay to preserve my headlight switch. They work great but now the auto-check system thinks my headlight bulb is out. Every time I turn on my headlights I get the defective headlight warning symbol. Does anyone know how I can prevent this? Wire in a resistor, perhaps? I did STFA and didn't find anything. Thanks.
01-13-2006, 08:08 PM
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Hmmm...
My car has had three different HID systems on it for over 5 years and I have never seen the headlight bulb thing, although I've heard about it on newer Audis. Not sure whether the previous owner might have done something before I had it. As far as I can see though, there are no relays anywhere for my headlights added in, and I've been through the wiring.
01-13-2006, 08:25 PM
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This is happening because the lamp control module (LCM) is not seeing the
required resistance (it is lower now that you have relayed it).
There is a way to modify the circuit board inside the LCM (which is located in the relay box under the hood) to "fooling" the auto-check.
If I can locate the write-up, I'll post it.
There is a way to modify the circuit board inside the LCM (which is located in the relay box under the hood) to "fooling" the auto-check.
If I can locate the write-up, I'll post it.
01-13-2006, 08:33 PM
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Lobotomizing the Autocheck Lamp Warning Module
from urs4.com
Phase 3: Lobotomize the autocheck lamp warning module
For the auto enthusiast who can't discern that a headlight has burned out, Audi has thoughtfully equipped the car with a warning system that beeps and displays a yellow X-ed out bulb in the autocheck display. The lamp warning module on the UrS4 is a complex piece of kit located in the main relay box in the plenum under the hood. It also warns for burnt out taillights and brake lights, which is a useful feature. The headlight warning circuit consists of two precision resistors and an IC which compares microcurrents across the headlight bulb filaments. Since the ballasts have a
different resistance than H1 bulb filaments, the autocheck will drive you to distraction unless you make like a neurosurgeon and lobotomize the thing. The procedure I used is based on Igor Kessel's excellent post in the Headlights section of urs4.com, here. Don your scrubbies, wash up, and let's begin.
1. Remove the lamp warning module and gurney it to the operating table. It looks like a double-wide relay and is located in the main relay box under the hood.
2. Remove the cover from the module. Locate the precision resistors for the headlight comparator (Photo L1).
<img src="http://web.archive.org/web/20030414070933/urs4.com/technical/HID/Photo+L1++Precision+resistors.jpg">
The terminals for the headlights are tagged 56bl, 56bl1, 56br, 56br1. It is easy to locate them by turning over the board and following the foil traces from the resistor joints.
3. Flip the board over and locate the solder joints for the resistors and the terminals connected to the resistors. We are going to short out each resistor by soldering together the terminal joints at the bottom of the board and isolate the resistors from the IC by cutting the foil traces on the board with a scalpel (or reasonable facsimile - I used an Olfa knife). You may want to cut the traces in an area which makes it easy to re-join them in case you want to restore the autocheck operation when you reach your dotage. Photo L2 shows the board with the modifications complete. Make sure the traces are well cut or the autocheck will still activate, usually on bumpy roads.
<img src="http://web.archive.org/web/20030414073319/urs4.com/technical/HID/Photo+L2+board+mods.jpg">
4. Reassemble the module, insert it in the car, and test. Blessed silence! The operation is a success! The patient is blissfully unaware of the Frankenlamps lurking under the hood! Bwaaahahahahaah!!
5. Enjoy your new high-tech lights
Phase 3: Lobotomize the autocheck lamp warning module
For the auto enthusiast who can't discern that a headlight has burned out, Audi has thoughtfully equipped the car with a warning system that beeps and displays a yellow X-ed out bulb in the autocheck display. The lamp warning module on the UrS4 is a complex piece of kit located in the main relay box in the plenum under the hood. It also warns for burnt out taillights and brake lights, which is a useful feature. The headlight warning circuit consists of two precision resistors and an IC which compares microcurrents across the headlight bulb filaments. Since the ballasts have a
different resistance than H1 bulb filaments, the autocheck will drive you to distraction unless you make like a neurosurgeon and lobotomize the thing. The procedure I used is based on Igor Kessel's excellent post in the Headlights section of urs4.com, here. Don your scrubbies, wash up, and let's begin.
1. Remove the lamp warning module and gurney it to the operating table. It looks like a double-wide relay and is located in the main relay box under the hood.
2. Remove the cover from the module. Locate the precision resistors for the headlight comparator (Photo L1).
<img src="http://web.archive.org/web/20030414070933/urs4.com/technical/HID/Photo+L1++Precision+resistors.jpg">
The terminals for the headlights are tagged 56bl, 56bl1, 56br, 56br1. It is easy to locate them by turning over the board and following the foil traces from the resistor joints.
3. Flip the board over and locate the solder joints for the resistors and the terminals connected to the resistors. We are going to short out each resistor by soldering together the terminal joints at the bottom of the board and isolate the resistors from the IC by cutting the foil traces on the board with a scalpel (or reasonable facsimile - I used an Olfa knife). You may want to cut the traces in an area which makes it easy to re-join them in case you want to restore the autocheck operation when you reach your dotage. Photo L2 shows the board with the modifications complete. Make sure the traces are well cut or the autocheck will still activate, usually on bumpy roads.
<img src="http://web.archive.org/web/20030414073319/urs4.com/technical/HID/Photo+L2+board+mods.jpg">
4. Reassemble the module, insert it in the car, and test. Blessed silence! The operation is a success! The patient is blissfully unaware of the Frankenlamps lurking under the hood! Bwaaahahahahaah!!
5. Enjoy your new high-tech lights
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01-13-2006, 08:35 PM
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