What is a Xenon HID Ballast?
A Xenon HID ballast is an electronic control unit that regulates the high voltage needed to ignite and maintain a Xenon (HID) bulb. Without a functioning ballast, your Xenon headlights simply won't work. Ballasts are typically located inside or directly behind the headlight assembly and are a common failure point on vehicles aged 8+ years.
Signs of a Failing HID Ballast
- One headlight flickering or cutting out intermittently
- Headlight takes longer than usual to illuminate
- Colour difference between left and right headlights
- Headlight warning light on the dashboard
- Headlight not turning on at all
Which Vehicles Use HID Ballasts?
Xenon HID lighting is factory-fitted to a wide range of European vehicles, including:
- Audi Q7 (2007–2009) — OEM part 63117180050
- BMW 1 Series F20/F21 (2010–2015) — OEM part 63117316145
- BMW 4 Series F32/F33/F36/M4 (2012–2017) — OEM parts 63117533073 / 63117316187
- Citroen C4 and C5
- Renault Clio, Laguna, Megane, and Espace
- Volkswagen Passat
- Volvo V70, XC70, and XC90
How to Replace a HID Ballast
Replacing a Xenon ballast is a straightforward job that most home mechanics can tackle with basic tools.
- Identify the faulty side — confirm which headlight is affected.
- Source the correct OEM replacement — match your vehicle's part number to ensure compatibility.
- Disconnect the battery — always disconnect the negative terminal before working with headlight electrics.
- Remove the headlight assembly if necessary — on some vehicles the ballast is accessible from the engine bay; on others the headlight must come out.
- Unplug the ballast connector — squeeze the tab and pull firmly.
- Unscrew and remove the old ballast — typically two or three bolts.
- Fit the new ballast — plug in the connector and secure with bolts.
- Reconnect the battery and test — the headlight should illuminate immediately.
OEM vs Aftermarket Ballasts
We always recommend OEM-specification replacement ballasts. Cheap aftermarket alternatives often fail prematurely and can damage your Xenon bulbs. Our OEM ballasts are direct plug-and-play replacements that meet or exceed the original manufacturer's specification.
Shop HID Ballasts at MI Lights
We stock a wide range of OEM Xenon HID ballasts for Audi, BMW, Citroen, Renault, Volvo, and Volkswagen vehicles. Fast UK delivery, with expert support available if you need help identifying the right part for your car.