The ballast is needed to trigger and operate a D2S / D2R Xenon lamp fitted to a 12 volt electrical system. To trigger the lamp the ballast produces a high voltage of approx. 23,000 volt. At the same moment it adjusts the current flow through the lamp to 2.5 A and the maximum power of 70 watt. After triggering , during operation, the ballast adjusts the lamp power of 35+/- 1 watt. The lamp voltage is then between 67 and 112 volt.

To ensure good operating condition the ballast works only when it receives 9 to 16 volt supply voltage. To prevent any damage to the ballast, the ballast switches off if the lamp is not operating after attempting to trigger it 4 times. Additionally a safety device, like a trip switch in household electrics, is installed.

Effects of failure

A faulty ballast causes a total loss of the headlamp operation. Causes for the failure can be the following:

Faulty supply voltage
Faulty ground/earth
Faulty xenon ballast
Faulty xenon lamp
Internal short-circuit
Diagnostics

For fault recognition consider the following check steps:

Check for triggering attempts of the ballast after switching on the headlamps. If triggering attempts fail the xenon lamp should be renewed.
If no trigger attempts are carried out, the fuse should be checked.
If the fuse is fine, check for voltage and ground/earth at the ballast. The minimum voltage must be 9 V and maximum 16 V.
If the voltage, ground and the xenon lamp are fine, a faulty ballast is the cause of the failure.
Important note: During the supply voltage check, the ballast must be securely connected to both lamp and supply connector. While working on the xenon lamp, the ballast must be disconnected to prevent any electrical shocks.