These would require a smart canbus system. If you have tried changing the bulb and it is still not illuminating then chances are you have had a ballast fail. Single Beam or Bi-Xenon Use.
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2 Lights Bicycle Lights Front and Rear Bicycle Led Lights Flashlight Rechargeable Bicycle Lights Bicycle Road Bicycle Lights Bicycle Accessories Bicycle Light Set
Aliexpress UK
Compatible With: H4 / P43T / 472 High / Low Beam. 2 x High Power LED Headlights Bulbs+ 2 x Wedge bulb 501 (W5W). Wedge bulb type: 501 (W5W). Beam Angle: 360°. Application: High/Low Beam Head Lights. To Fit: High/Low Beam Head Lights KIt.
eBay
Bicycle Light Front and Rear Bicycle Led Light Flashlight Rechargeable Bicycle Light Bicycle Road Bicycle Light Bicycle Accessories Bicycle Light Set
Aliexpress UK
H4 High / Low Beam. Wedge bulb type: 501 (W5W). 2 x High Power LED Headlights Bulbs+ 2 x Wedge bulb 501 (W5W). Beam Angel: 360 Degrees. Beam Angle: 360°. To Fit: High/Low Beam Head Lights KIt. Application: High/Low Beam Head Lights.
eBay
BUCKLOS 3D Printed Carbon Saddle MTB Road Bike Saddle Seat For Bicycle Hollow Light Weight Bike Seat Cushion Bike Accessories
Aliexpress UK
Headlight bulb type: H4. Beam pattern: Surround glow. Technology: Xenon. Important notice: The compatibility chart above is for guidance only. All our bulbs are sourced from quality suppliers. Colour: Yellow.
eBay
T6 LED Bike Light USB Rechargeable Bicycle Lights Front 6 Modes MTB Flashlight Bicycle Headlight for Cycling Bicycle Front Lamp
Aliexpress UK
Type: Bike Light. Light Color: 6 Colors for You Choose. Due to the light and monitors effect, colors may have lightly difference.
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Seraph-Carbon Gravel Bike Frame, Super Light Bicycle Cycle, XS GR047, T1000, girl frame , chameleon bike frame , cycle
Aliexpress UK
Argo's H4 xenon bulbs are an ideal choice for enhancing your lights. With their intense light output and ultimate power, they provide a significant upgrade to your car's lighting system. The xenon gas allows the bulbs to burn considerably brighter than standard halogen bulbs.
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2 T6 LED Bike Light Type-C Charging Bicycle Lights Front 6 Modes MTB Flashlight Bicycle Headlight for Cycling Bicycle Front Lamp
Aliexpress UK
Argo's H4 xenon bulbs are an ideal choice for enhancing your lights. With their intense light output and ultimate power, they provide a significant upgrade to your car's lighting system. The xenon gas allows the bulbs to burn considerably brighter than standard halogen bulbs.
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Gaciron Bicycle Front Light,Raptor 1800/3000 Lumens Wireless Remote Control Bike Headlight,Auminium Anti-Glare Bike Front Light
Aliexpress UK
Color Temperature： 6000K White. Wedge bulb type: 501 (W5W). H4 High / Low Beam. 2 x High Power LED Headlights Bulbs+ 2 x Wedge bulb 501 (W5W). Beam Angel: 360 Degrees. Beam Angle: 360°. To Fit: High/Low Beam Head Lights KIt.
eBay
X-TIGER Bike Light Rainproof With Power Bank Rechargeable LED Lamp 4000mAh MTB Front Lamp Headlight Aluminum Bicycle Light
Aliexpress UK