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Using the Bosch E46 Bixenon Ballasts

The BMW E46 with bixenon headlights came with specific Bosch ballasts which not only provided the high-voltage power to the xenon bulbs like in any HID system, but also had a circuit for controlling the 3-wire projectors on this car. Many people who buy the E46 bixenon projectors on Ebay or elsewhere buy only the bare projectors, and don't get the matching ballasts from the same car. This is why I made my interface boards which you can buy here. But if you happened to get these ballasts, then you don't need my circuits. On this page, I'll show you how to hook up your Bosch ballasts to properly trigger the high-beam solenoids.

First, let's make sure you have the proper ballasts. The E46 came with both single and bixenon options, and the single-xenon version has a slightly different ballast, which doesn't have the connections needed to trigger the solenoids. Below are two pictures of the Bosch bixenon ballast.

Bosch bixenon ballast
Bosch bixenon ballast
Bosch Bixenon Ballast

Notice that there are two input connectors, and two output cables. The single-xenon version of this ballast looks much the same, except there is only one output cable.

The photo below shows how the ballast is connected in the complete system. On the right is the ballast; there are two sets of 3 wires exiting this ballast. One cable goes to the black box on the far left. This is called the "ignitor", which transforms the electricity from the ballast to a higher voltage, and in turn connects to the bulb with the red-and-black connector shown, which carries a high-voltage warning sticker. The other set of 3 wires connects to the solenoid at the bottom of the projector.

Bosch bixenon system
Bosch bixenon system

Here's a picture of the ballast powered on. The left terminal is connected to ground, and the right terminal is connected to +12V from my benchtop power supply with the red test lead.

Ballast powered on
Ballast Powered On

Here's a picture of the top of the ballast, showing the connections for both the main ballast power on the left, and the pin for activating the high-beams on the right. To get your high-beam ballasts working, all you have to do is make those three connections. The two on the left are already used for powering on the ballast for the low-beams, so the only additional wire you need is +12V for the high beams. Note, however, that the ballast must be powered on for the high-beam solenoid to work; you can't trigger the solenoid properly with the lights out (which would be useless anyway).

Ballast connections
Ballast Connections

Here's a diagram of the whole system, which should hopefully make this all more understandable.

Bixenon System
Bixenon System

Connecting to the power connector on the left is easy, since that's a standard 9006 connector used on most cars with separate high and low beams. This connector is easily available on Ebay, and possibly at your local auto parts store. The connector on the right is a BMW connector, but luckily you can purchase this from BMW. The part number for the plug is, and the part number for the contact bushing is If that's too much trouble, you can wire instead to one of the wires behind this connector. Here's a picture of what we see when we remove three screws take this ballast apart:

Ballast opened
Ballast Opened

That high-beam pin on the smaller connector connects to the red wire on the left, and if we follow that, it goes directly into the 3-wire cable which attaches to the solenoid. So all you have to do is cut the red wire going from the ballast to the solenoid, and connect it (on the solenoid side) to your switched +12V source.

How does the ballast properly activate the solenoids then? Only one wire, the black one, actually goes into the ballast; the red one connects to the 3-pin connector, and the green one connects to the ballast's main power connector as you can see in the picture. The ballast detects current flowing through the "pull" solenoid's ground when high-beams are activated, and then turns off that ground connection after a short time.

Finally, if you're wondering what those other two pins in the three-pin connector are for, I don't actually know. I believe they may be intended to connect to the E46's data bus, perhaps for diagnostic functions. However, I'm able to properly trigger the solenoid only with the middle pin as I just described, so it isn't essential to the operation of the ballast or the high-beam solenoid.