Quick answer
Replace a semi truck headlight when the lens is cracked, moisture gets inside, or output visibly yellows — all three fail DOT inspection criteria for adequate illumination. Match the assembly by your truck's model and year range plus the side (driver/passenger), and check whether your truck runs halogen or LED before ordering: the housings and connectors differ. An aftermarket direct-replacement assembly bolts to the factory points and plugs into the existing harness.
Cracked lens, yellowed housing, or time for an LED upgrade? What to check before ordering a headlight for a Kenworth, Peterbilt, Volvo or Freightliner.
Housing, bulb, or both?
"Headlight" can mean the complete housing assembly (lens, reflector, buckets, harness connector) or just the bulb inside it. A cracked or fogged lens, moisture inside the light, or crash damage means the assembly; a working housing that's simply dim may only need bulbs. Assemblies are sold per side — like mirrors, LEFT is the driver side and RIGHT is the passenger side, and the two are not interchangeable.
Halogen vs LED assemblies
- Halogen: lower purchase price, bulbs are cheap and everywhere, but shorter life and less light on the road.
- LED: brighter, whiter beam and a service life that typically outlasts several halogen bulb cycles — a real safety and downtime upgrade for night-heavy routes.
- Check the connector: many LED direct replacements plug into the factory harness, but verify the listing states plug-and-play for your truck. Some trucks need an anti-flicker/CAN resistor adapter.
- Make sure any assembly is DOT-compliant for on-road use — all headlight assemblies we sell are.
Match the body style, not just the model year
Truck makers change front-end sheet metal mid-generation, and aero and classic hoods on the same model take different lights. The reliable identifiers are the truck model PLUS hood style, and best of all the part number on the back of the old housing — search that cross-reference in our catalog, or filter the Headlights category by your truck make.
Aim them after you install them
A perfectly good headlight aimed high blinds oncoming drivers; aimed low it wastes half your visibility. After swapping housings, park on level ground facing a wall and set the beam cutoff per your truck's service guidance — five minutes that makes the upgrade actually pay off.
Frequently asked questions
Can I get a DOT violation for a bad headlight?
Yes — inoperative or badly degraded headlamps are an out-of-service-level violation under FMCSA regulation 393.24, and moisture or heavy hazing that cuts output can be written up at inspection. It's one of the cheapest violations to prevent.
Halogen vs LED headlight — which should I buy?
LED assemblies last longer, draw less power and light the road better, but cost more upfront and must match your truck's harness. If your truck came with halogen, a direct-replacement halogen assembly is the plug-and-play choice; LED upgrades exist for popular models — verify the connector before ordering.
How do I make sure a part fits my truck?
Use the free VIN lookup at partstop.net/vin (parts verified against your truck's build data), match the OEM / cross-reference number from your old part, or call (253) 600-1351 — fitment is checked before you buy.
How fast does PartStop ship?
In-stock orders placed before the daily cutoff ship the same business day (Monday–Saturday) from Tacoma, WA. Standard delivery typically takes ~3 business days, free on orders over $100; overnight is available on most items ($50 small / $150 medium / $300 large parcel).
Shop related parts
Premium-quality aftermarket direct replacements — nationwide same-day shipping, 6+ month warranty.
Need the part, not just the reading?
Every part below is a Premium Quality aftermarket Direct Replacement with published OEM cross-reference numbers, a 6+ month warranty and same-business-day shipping from Tacoma, WA. Not sure it fits? Run your VIN — or call and a person who knows trucks will verify fitment before you pay.