Buy GMC Sierra 1500 Headlight Assembly

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Overview

The GMC Sierra 1500's headlight (also called a headlamp, front lamp, or light assembly) keeps the road bright and helps on-coming drivers see you. Across the 1999-2025 model years, Sierra pickups have used halogen, HID, and-more recently-factory LED beam units. Most trims share the same basic job steps for bulb swaps, aiming, cleaning, and wiring checks. Key points:

• Bulb sizes changed over the generations (early trucks use 9005/9006, mid-generation trucks use 9012 dual-beam, and the newest trims use integrated LEDs).
• Moisture, poor ground wires, and aiming mistakes cause most head-beam complaints-not burned-out bulbs.
• U.S. law (FMVSS 108) and SAE J1383 set light-output limits; wrong upgrades can be illegal.
• GM has issued service bulletins and at least one recall related to poor performance and glare.

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Fitment Guide

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Fog/DRL sizes: most fourth-gen trucks use 5202 fog bulbs, while earlier trucks used H10/9145.

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Light Types

Halogen

Standard 55 W bulbs (9005/9006 or 9012) are inexpensive and easy to swap.

HID

Several owners retrofit HID capsules, but aim is critical; too much glare violates FMVSS 108.

LED

Factory LEDs (2019+) run cooler and last longer but the whole lamp must be replaced if a diode fails.

Tip: Choose replacements marked "DOT/SAE" so they meet brightness rules set by SAE J1383.

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Common Problems

• Condensation: A failing lens seal lets damp air in. Dry the unit with a low-heat hair-dryer, then reseal or replace the gasket.
• Water-intrusion shorts: GM bulletins link trapped water to battery drain and flicker; inspect the X110/X120 connectors for corrosion.
• Poor output on dark roads: GM's bulletin PIT5374 offers a BCM software update plus higher-quality bulbs for 2014-15 trucks.
• Glare complaints (2010-17 Terrain case): GM fixed excessive glare with an applique sticker-proof that correct beam cutoff matters.

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DIY Install

1. Open the hood and pull the upper radiator-cover pins.
2. Remove the retaining bolt and slide the headlight straight forward. A simple walk-through video shows the full swap on a 2014 truck. Watch it here
3. Twist the bulb counter-clockwise, swap it, and avoid touching the glass.
4. Re-seat the lamp; tighten the bolt to about 71 lb-in (8 N·m) if you removed the DRL diode bracket.

Tools: T15 Torx, 10 mm socket, flat trim tool, latex gloves.

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Maintenance

• Cleaning hazy lenses: Wet-sand (1000/2000 grit) → polish → UV-seal.
• Seal check: After storms, look behind the lamp; droplets mean the vent or seal has failed.
• Fuse & relay: Headlight fuse is in the under-hood block (see YouTube guide). View location
• Aiming: Park 25 ft (7.6 m) from a wall, mark lamp centers, then turn the vertical adjuster with a T15 until the cutoff hits the tape. Quick demo video here. Adjusting guide

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Legal & Safety

• U.S. rule FMVSS 108 sets minimum and maximum candlepower plus mounting height. Read the summary on the FHWA site. FMVSS 108 overview
• SAE J1383 describes photometric tests engineers use to certify head-beams. SAE page
• Before selling a truck, check open recalls with the NHTSA VIN tool. Recall lookup

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Upgrades & Mods

• LED projector assemblies (fits 2014-18) give 5000 K DRLs and plug-and-play wiring.
• 12-pin harness conversion: Forum users mapped the Sierra 1500's 2023 pin-out for custom lights-see the wiring diagram here. Diagram thread
• Anti-flicker drivers stop "bulb-out" warnings on trucks with factory PWM circuits.
• Trail ready coating: Clear film keeps rocks from pitting the lens.

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Troubleshooting

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New Section:

Q: What bulb does a 2014 Sierra 1500 use?
A: One 9012 dual-filament bulb handles both low and high beams.

Q: How about a 2007 classic truck?
A: It uses a 9006 low-beam and a 9005 high-beam in separate reflectors.

Q: My lights look hazy. Can I fix them myself?
A: Yes-sand, polish, and seal the lenses, or install new lamp assemblies.

Q: There's water inside the housing. Is that normal?
A: A light mist can appear in cool weather, but standing drops mean the seal is leaking; dry it with a hair-dryer and reseal.

Q: How do I aim the beams?
A: Park 25 ft from a wall, mark center height, turn the T15 screw until the cutoff sits just below the tape line.

Q: Are aftermarket LEDs legal?
A: Only if they carry DOT/SAE marks and do not exceed FMVSS 108 limits.

Q: Why did GM recall some headlights for glare?
A: Certain GMC Terrain units exceeded the 125 cd cutoff; GM added a lens appliqué to reduce brightness.

Q: My new bulb still won't light-now what?
A: Check the socket for burnt pins and the ground wire; corrosion can stop current.

Q: What torque should I use on the support bolt?
A: About 71 lb-in (8 N·m) keeps the lamp snug without cracking plastic.

Q: Can I wire DRLs into the headlights?
A: Yes-use the brown "park" wire on the 12-pin harness per the forum pin-out.

Q: Where is the headlight fuse?
A: In the under-hood fuse block-look for F34UA or F39UA depending on model year.

Q: Do headlights self-level?
A: Sierra 1500s do not have auto-leveling; aiming remains manual but is usually preset at the factory.

Q: What's the safest color temperature for upgrades?
A: Around 5000-6000 K mimics daylight without reducing wet-road contrast.

Q: Will brighter bulbs melt the housing?
A: Stick to bulbs within the wattage listed in the owner's manual; higher wattage can over-heat reflectors.

Q: Can condensation damage electronics?
A: Yes-water can short the internal DRL driver and drain the battery, so fix leaks quickly.

Q: How long do LEDs last?
A: Factory LED modules often exceed 10 years, but integrated units mean replacing the full lamp if they fail.

For deeper reading, visit these helpful pages: GM authority recall article | Wiring diagram forum | DOT headlight rules.