Headlight Faults & Help

Headlight Faults & Help - Diagnose & Fix Car Lighting Problems

If your car headlights are not working correctly, flickering, or switching off, this guide will help you identify the cause and find the right fix.

At HIDS-DIRECT, we specialise in diagnosing and supplying solutions for common lighting faults including xenon (HID), LED and halogen systems.

Common Headlight Problems

• Headlight not turning on
• Light flickering or intermittent
• Headlight turns on then switches off
• One headlight dimmer than the other
• Dashboard warning messages

These issues are usually caused by one of three components: the bulb, the ballast (HID systems), or wiring/control modules.

Replacement Parts for Headlight Faults

If your headlight fault has been identified, you can browse all compatible replacement components including xenon ballasts, igniters, LED modules and AFS control units below:

View Ballasts, Igniters & Control Modules

Xenon (HID) Headlight Faults

Signs of a Faulty Xenon Ballast

• Headlight not working at all
• Light ignites briefly then switches off
• Flickering during use

The ballast controls the ignition and power supply to the xenon bulb. When it fails, the bulb will not operate correctly even if it is new.

Browse Xenon Ballasts & Modules

Signs of a Faulty Xenon Bulb

• Purple or pink colour change
• Dim output
• Delayed ignition

Browse Xenon Bulbs

LED Headlight Faults

• Flickering LED bulbs
• Dashboard error messages (CANBUS issues)
• Bulb not recognised by vehicle

These issues are often caused by compatibility or CANBUS sensitivity in the vehicle.

Browse LED Headlight Bulbs

Halogen Headlight Issues

• Bulb blown
• Loose connection
• Wiring or fuse issues

Halogen faults are usually simple and resolved with a replacement bulb.

Browse Halogen Bulbs

How to Diagnose the Problem (Quick Test)

Swap Test Method

One of the easiest ways to diagnose a headlight fault is to swap components from left to right:

• If the fault moves - the part is faulty
• If the fault stays - wiring or headlight unit issue

This method works well for bulbs, ballasts and control modules.

Using Diagnostic Tools for Headlight Faults

Diagnostic tools such as iCarsoft scanners can help identify headlight faults by reading error codes and checking communication between the vehicle and lighting control modules.

They are useful for confirming whether a ballast, LED module or control unit is faulty before replacing parts.

View iCarsoft Diagnostic Tools

Note: Most aftermarket diagnostic tools do not support coding or programming of new headlight modules. In some cases, dealer-level equipment may be required for initialisation or advanced configuration.

When It’s Not the Bulb or Ballast

If replacing bulbs or modules does not fix the issue, the problem may be:

• Headlight control module
• Wiring fault
• Vehicle ECU communication issue

In these cases, diagnostic tools may be required.

Need Help Finding the Right Part?

If you are unsure what part you need, we can help.

• Send us your registration or VIN
• Or send a photo of your existing part number

Our team will help you identify the correct replacement quickly.

Headlight Fault FAQ

Why does my xenon headlight turn on then off?

This is commonly caused by a failing ballast. The unit may ignite the bulb but cannot maintain a stable power supply.

How do I know if it is the bulb or the ballast?

The easiest way to check is to swap components from left to right. If the fault follows the part, that component is faulty. If the fault stays on the same side, it may be wiring or a headlight unit issue.

Why is one headlight dimmer than the other?

This is often caused by an ageing xenon bulb or a failing ballast. Xenon bulbs can change colour and brightness over time, while a weak ballast may not supply consistent power.

Do LED headlight bulbs cause dashboard errors?

Some vehicles are sensitive to LED conversions and may display CANBUS error messages. Using high-quality, vehicle-compatible LED bulbs usually resolves this issue.

Can a diagnostic tool fix a headlight fault?

Diagnostic tools can help identify headlight faults by reading error codes and checking module communication. However, most tools do not perform coding or programming of new headlight modules.

Can I fix a headlight fault myself?

In many cases, yes. Replacing bulbs or ballasts is often straightforward and plug and play. More complex issues such as wiring faults or control module problems may require professional diagnosis.