HERCOO Light Module for GM GMT800 Trucks — 2003–2007 Chevy/GMC, 8-High Fog/Low/High/DRL Sync, Plug-and-Play

HERCOO's compact 8-high light module lets low beams, high beams, fog lamps and DRL operate together for improved forward visibility on compatible Chevy and GMC GMT800 trucks.

This small plug-and-play circuit board is engineered to work with many Silverado, Sierra, Tahoe and Escalade models from the 2003–2007 era. It reroutes factory headlamp relays so your front lighting elements light simultaneously when you activate the high beams, giving fuller illumination without cutting or splicing factory wiring. The unit is made on a durable FR-4 PCB and installs quickly in the relay/fuse box—no permanent vehicle modifications required.

Which vehicles will this module fit?

The HERCOO light module is designed for GMT800 family vehicles and closely related models from the 2003–2007 production years. Confirm compatibility with the list below and by checking your vehicle’s relay labels before purchase.

• Chevrolet Silverado 1500/2500/3500 (2003–2007, including HD and Classic variants)
• GMC Sierra 1500/2500/3500 (2003–2007, including HD and Classic)
• Cadillac Escalade, Yukon, Tahoe, Avalanche, Escalade EXT (2004–2006 and select years listed)
• Specific fitments include GMT800 trucks and a range of 2003–2006 GM full-size models—verify relay labels Hdlp-Hi, Hdlp-Low, Fog Lp, DRL

How does this module change my vehicle’s lighting behavior?

When installed, the module allows low beams, high beams, fog lights and daytime running lights to illuminate together whenever the high beams are on. Normal operation remains unchanged when high beams are off—low beams, fog lamps and DRL work as factory intended.

• High-beam activation also triggers fog lamps and DRL for maximum front illumination
• No interruption to stock lamp function during normal (non-high-beam) driving
• Improves forward coverage on dark roads and in low-visibility conditions

How simple is installation and what do I need?

Installation is quick and reversible—no cutting, soldering or wire splicing required. You just access the vehicle’s fuse/relay box and swap relays around the small circuit board so each factory relay plugs into the module in its original position.

• Tools: basic access to the relay box; no special tools typically needed
• Time: most installations take under five minutes once the relay box is located
• Procedure: remove relays labeled Hdlp-Hi, Hdlp-Low, Fog Lp and DRL, place the board, then reinstall relays

What is the module made of and is it reliable?

The unit uses FR-4 printed circuit board material for a robust, heat-resistant structure. Its compact design is intended for the vehicle’s relay area and built for routine road use; proper relay seating and a secure relay box cover are recommended for long-term reliability.

• FR-4 PCB offers durability and stable electrical performance
• Engineered to work with factory relays—no rewiring required
• Comes as a single high-performance circuit board with support from the seller

Who is this for: The HERCOO 8-high light module is ideal for owners of compatible Chevy and GMC GMT800 trucks and related GM SUVs who want stronger front illumination without permanent wiring changes. It suits drivers who frequently travel dark rural roads or face poor visibility and who prefer a simple, reversible upgrade that keeps factory components intact.