The Valeo compatible control unit with code 73930912 is a ballast (or control unit) for Xenon headlights . It is manufactured by Valeo and is compatible with various car brands, including Audi, BMW, Citroën, Opel, Seat, Skoda, Volkswagen and Renault (for example, for the Laguna II).

What is it for?

The 73930912 control unit has the fundamental task of managing the operation of xenon lamps . Unlike traditional halogen lamps, xenon lamps cannot be powered directly from the vehicle's battery. They require a very high ignition voltage (tens of thousands of volts) to ignite and a precise and stable voltage and current to maintain the electric arc once ignited.

Specifically, this control unit performs the following functions:

• Ignition: Generates the high voltage needed to ignite the electric arc inside the Xenon lamp.

• Power supply (Ballast): Once the lamp is turned on, the control unit stabilizes the voltage and current, ensuring that the lamp operates at the correct power and without flickering.

• Protection: Protects the lamp and the vehicle's electrical system from overloads or short circuits.

• Diagnosis: In some cases, it can communicate with the vehicle's main control unit to report any malfunctions.

Why replace the 73930912 control unit?

Replacing this control unit is necessary when problems occur with the functioning of the xenon headlights. The most common reasons for failure include:

• Headlights that don't come on: If one or both of your Xenon bulbs don't come on at all, even after checking that the bulb itself is intact, the problem is most likely the control unit.

• Headlights flickering or going out: If your Xenon lights come on but then flicker, dim, or suddenly go out while driving, it's a clear sign of a ballast malfunction.

• Light intensity variations: If the brightness of the headlight varies abnormally, the ballast may not be able to maintain a stable current.

• Dashboard Errors: The vehicle may report a lighting system error (e.g., “Headlights Malfunction,” “Check Lights”), indicating a ballast problem.

• Water or Moisture Ingress: Water or moisture can enter the control unit and damage the internal electronic components, causing short circuits or corrosion.

• Wear and tear of internal components: Over time and with use, the electronic components of the control unit (such as capacitors, transistors or relays) can degrade and fail.

• Short circuits or surges: Problems in the vehicle's electrical system or power surges can irreversibly damage the ballast.

In many cases, replacing just the control unit is a much more cost-effective solution than purchasing and installing a new headlight, especially if the headlight is intact and the problem is merely electronic. It's important to ensure the ballast is replaced with a compatible, quality replacement to ensure the proper functioning and safety of the lighting system.

Compatible cars:

• Alfa Romeo 166 1998, 1999, 2000, 2001, 2002, 2003
• Audi A4 S4 B5 1997 - 2002
• Audi A4 S4 B5 B6 Sedan Sedan Avant
• Citroën C5 DC DE 2001, 2002, 2003, 2004
• Citroën C8
• Peugeot 607
• Peugeot 807
• Renault Laguna MK2 2001, 2002, 2003, 2004
• Renault Espace MK3 1997, 1998, 1999, 2000, 2001, 2002, 2003
• Renault Safrane
• Fiat Ulysse
• Volkswagen Lupo 6E 1999-2006