Car Bulb Finder

Understanding Car Bulb Types

Common Bulb Numbering Systems

Automotive bulbs use several numbering systems depending on region and application. The most common are: BAU/BA15s numbers (e.g., 346, 286), festoon numbers (e.g., 269, 209), and halogen codes (e.g., H4, HB4, 9006).

12V vs 24V Bulbs

12V bulbs: Standard for cars, motorcycles, and light commercial vehicles

24V bulbs: Used in trucks, buses, heavy commercial vehicles, and some agricultural equipment

Important: Always use the correct voltage for your vehicle. Using 12V bulbs in a 24V system will result in dim lights and shortened bulb life. Using 24V bulbs in a 12V system means they won't illuminate properly.

Popular Bulb Types by Number

346 Bulb (24V - 21W): BA15d base, commonly used for stop/brake lights and indicators in trucks and commercial vehicles. Twin filament design.

508 Bulb (24V - 1.2W): Dashboard and instrument panel lighting in 24V vehicles. Very small wedge-type bulb.

286 Bulb (12V - 1.2W): Dashboard panel lights, speedometer illumination, small indicator lights in cars.

290 Bulb (24V - 21W): Heavy duty applications - brake lights, reverse lights, indicators in trucks and commercial vehicles.

233 Bulb (12V - 4W): Side lights, tail lights, number plate lights in cars. BA9s base.

504 Bulb (12V - 3W): Side lights and parking lights. Capless wedge design.

507 Bulb (24V - 5W): Side tail lights in commercial vehicles and trucks.

921 Bulb (12V - 16W): Reverse lights, brake lights. Wedge base design.

Halogen Headlight Bulbs

H4 Bulb: Dual filament (high/low beam) halogen headlight bulb. Most common worldwide. Power: 60/55W or 75/70W

HB4 (9006) Bulb: Single filament low beam or fog light bulb. Power: typically 51-55W. Common in Japanese and American vehicles.

475 Bulb: H4 type headlight bulb, available in different wattages for various applications.

Bulb Base Types

• BA15s: Single contact bayonet (15mm diameter) - used for indicators, brake lights
• BA15d: Double contact bayonet (15mm) - dual filament bulbs
• BAY15d: Offset pins bayonet - prevents incorrect installation
• BA9s: Small bayonet (9mm) - side lights, dashboard
• Wedge: Push-in design without base - dashboard, interior lights
• Festoon: Cylindrical with contacts on ends - interior, number plate

When to Replace Bulbs

• Bulb has failed completely (no light)
• Light output is significantly dimmed (replace both sides for even illumination)
• Bulb is flickering intermittently
• Glass envelope is darkened or discolored
• Annual check recommended for critical safety lights
• Always replace bulbs in pairs (headlights, indicators) for consistent light output

Bulb Replacement Tips

• Never touch halogen bulb glass with bare hands - use gloves or cloth
• Disconnect battery before replacing bulbs in modern vehicles with complex electronics
• Check for correct voltage (12V or 24V) before installation
• Ensure bulb is securely seated and locked in position
• Test operation before reassembling light units
• Keep spare bulbs in vehicle for roadside replacements
• In many countries, driving with a failed headlight is illegal - replace immediately

LED vs Halogen Bulbs

Halogen bulbs: Traditional technology, lower cost, warm white light, higher power consumption, shorter lifespan (500-1000 hours)

LED bulbs: Modern alternative, higher initial cost, very long lifespan (15,000-30,000 hours), lower power draw, brighter and whiter light. Note: Some vehicles may require CANbus-compatible LED bulbs to avoid error messages.

Legal Requirements

All external lights must be working for MOT/roadworthiness testing. Regulations specify minimum light output and beam patterns. Using incorrect bulb types or wattages can result in MOT failure or fines. Headlight bulbs must be E-marked for legal road use in UK/EU.