Hello
I have a mercedes 202, got hold of some stock hid lights (the street legal ones, with all required aparatus), yes they were availlable when the car was being built, though still rare.
I managed to find some new old parts to install this upgrade.
Still missing is the wiring and the control module. 
-the sensors looks like simple potentiometer not very linear, but nothing that could not ba solved by and ohmeter and raising lowering the car. 
-Wiring the controler not a problem if I use the arduino.
-Driving the electric motors that do the job, is the problem >:(. I can only see 4 wires in the connector. So I guess it is a stepper motor (solution used nowadays by the industry) but which wire is which ?
How to test without frying it ?
Someone has experience with black box stepper motor ?
or should I sacrifice open one of the motor ?
regards
Philippe
Hey!
I dont know much about stepper motors...
Once i connected the cables to a (current limited?) 5V source according to a trial-and-error plan... it worked fine after some trying... 
Maybe an ohmmeter could tell u, between which cables is a single coil?
Maybe this tutorial or this thread can help u?
Bye
Use a ohmeter to get resistance between all combination of pairs. You will get different values, but repeating. Like 0.8, 1.6, 0.8, 2.4, 0.8...etc
Write down the lowest one, this will be the ONE COIL resistance. Check which pairs give this resistance, and you get they are the supply for ONE coil. Draw the schematic like this.
GREEN-^v^v^v-YELLOW-^v^v^v-RED.^v^v^v-BLUE-^v^v^v-->GREEN
and you get the transitions needed to drive it.
Tell me if you need more help after you get this done
Thank's, I have enough to start testing.
1 link the wires to the coils
2 energize the coils to see which way it moves
3 speed up, increase voltage, hope it does not burn, look for missed steps.
I'll post the results goog or bad.
Just one detail, you said you have 4 wires coming from the motor. It sounds like you might have a "star" configuration in the motor. I mean, you have a common wire for all coils, and three wires linking each coil.
In this case you will get the lowest resistance from that common coil to the others, and 2X resistante between all others.
Check that before. If it is not a star configuration, it is a 4 coil (not 3) motor, but I haven'tever seen a 4 coil stepper motor. I am not saying they don't exist, but I have never had the pleasure to get one...