Name: Repairius
Price: 99.99 USD

Quick-reference chart, upgrade notes, and replacement tips from an ASE-certified master tech

Quick reference

Location	Bulb Size	Type
Headlight — Low Beam	H11 (most common; halogen projector)	Halogen or LED assembly depending on spec
Headlight — High Beam	HB3/9005 (most common); some builds H9	Halogen reflector or LED assembly
Fog Light (bumper)	H11 (most common); some LED sealed lamp	Halogen or LED, trim-dependent
Daytime Running Light (DRL)	Integrated (no separate bulb on most US trucks)	BCM/PWM-controlled low or high beam; some LED headlamp DRL strip
Front Turn Signal / Parking	3157A/3457A (amber) in most halogen headlamps	Incandescent/LED depending on headlamp option
Rear Turn Signal	LED module (non-serviceable) on most tractors; some fleets use serviceable 3157/1157	LED or incandescent, body option dependent
Brake (Stop) Light	LED module (non-serviceable) on most; 3157/1157 on incandescent housings	LED or incandescent, body option dependent
Tail/Running (Rear)	LED module on most; 3157/1157 (dual-filament) on incandescent housings	LED or incandescent
Reverse (Back-Up)	LED module on most; 3156/921 common in incandescent housings	LED or incandescent
License Plate	194/168 (T10) wedge on most; some LED license lamp modules	Incandescent or LED
Side Marker/Clearance (cab/sleeper/fairings)	Sealed LED 2.5"/4" markers common; 194/168 in some serviceable housings	LED or incandescent, body option dependent
Interior Dome/Map (cab/sleeper)	194 (T10) wedge common for map; 31mm festoon or LED panel in some domes	Incandescent or LED

Notes:

Never rely solely on year/model for bulb selection. Kenworth offered multiple headlamp and body lighting packages in 2014. Confirm by VIN, by reading the bulb number molded on the lamp, or by removing the socket to inspect.
If your truck has factory LED headlamps or LED tail modules, individual bulbs are not serviceable; the complete lamp/module is replaced.

LED vs halogen upgrade considerations

Headlamps: The T680’s halogen projector low beam (commonly H11) can accept quality H11 LED retrofits, but light pattern and glare control vary. Projector optics help, yet not all LED H11s aim correctly. Consider a full OEM-style LED headlamp assembly if available for your VIN for best beam control and durability.
CANBUS/PWM: The T680’s lighting circuits are BCM/PWM monitored. LED retrofits (especially turn signals, DRL/high-beam circuits used as DRL, and license lamps) may cause hyper-flash or bulb-out warnings. Use CANBUS-ready LEDs or add load resistors/anti-flicker modules rated for heavy-duty 24V equivalent current handling as required by your build (many T680s are 12V systems—verify before adding resistors).
DRL behavior: If your truck uses high or low beams as DRL via PWM, some LED bulbs will flicker. An inline anti-flicker decoder or switching to a dedicated LED headlamp assembly solves this.
Heat and space: Headlamp rear caps can be shallow. Check LED heat sink clearance, and ensure caps seal to keep dust/moisture out.
Legality: Ensure any LED headlamp or bulb carries appropriate DOT/SAE markings for on-road use.

Low beam (H11 projector): Turn wheel inward for access, remove rear dust cap on headlamp, rotate H11 bulb counterclockwise, disconnect, install new without touching glass. Re-seat cap to seal.
High beam (HB3/9005 or H9): Access rear of headlamp, rotate bulb counterclockwise, swap. Verify connector keying (HB3 vs H9 differ). Aim check after replacement.
Fog light (H11): From beneath or via bumper access panel, rotate socket out, replace H11. Confirm O-ring seats to keep moisture out.
DRL: No separate bulb on most; DRL uses headlamp filament/LED. Address at headlamp as above.
Front turn/parking (3157A/3457A): Twist the amber socket from the headlamp housing, pull dual-filament bulb straight out, install amber (A/NA) bulb. Test for hyper-flash if using LED.
Rear stop/turn/tail: If LED module, remove fasteners and replace entire lamp. If incandescent housing, twist out socket and replace 3157/1157 dual-filament as equipped.
Reverse: On LED modules, replace the module. On incandescent housings, remove socket and install 3156 (single) or 921 wedge as fitted.
License plate (194/168): Remove lens screws, pull the T10 wedge bulb, push in new bulb. Ensure gasket/lens reseals.
Side marker/clearance: Most are sealed LED; replace the complete 2.5" or 4" marker with like-for-like. Serviceable markers may use 194/168—pull lens and swap.
Interior dome/map: Pry lens carefully, replace 194/T10 wedge in map lights. Sleeper/cab domes may use a 31mm festoon or an LED panel—match the original.

Tips:

Disconnect batteries when working around lighting harnesses to avoid BCM faults. Use dielectric grease on exterior bulb sockets and check grounds.
Always verify polarity on LED wedges/festoons; flip 180° if they don’t light.

Moisture intrusion in headlamp or fog housings leading to short bulb life; reseal dust caps and replace cracked lenses.
Hyper-flash or bulb-out warnings after LED retrofits due to low current draw; resolve with CANBUS-ready lamps or proper load resistors.
Headlamp lens haze/yellowing reducing output; restore lenses or replace assemblies.
Ground and connector corrosion at frame rails and behind bumper causing intermittent rear lamp operation; clean/repair grounds and apply dielectric grease.
PWM-related flicker on DRL with some LED bulbs; add anti-flicker modules or revert to compliant halogen/LED assemblies.
Clearance/marker water ingress on cab roof and fairing lamps; replace gaskets or upgrade to sealed LED markers.

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