2018 Ram 1500 — Bulb Sizes (Headlight, Tail, Fog)

Quick reference

Notes

• 2018 Ram 1500 came with two main headlamp styles: Quad reflector halogen (common on Tradesman/SLT/Big Horn/Lone Star) and Projector halogen (Sport/Laramie/Longhorn/Limited). No factory HID/Xenon headlamps in 2018; some trims added factory LED fogs and LED tail lamps.
• Bulb calls above reflect the most common configurations. Always verify by visual inspection or VIN, especially for special editions (Rebel, Night, Black, etc.).

LED vs halogen upgrade considerations

• CANBUS and PWM: The 2018 Ram 1500 uses a CANBUS with pulse‑width modulation for lamp monitoring. Many LED replacements (headlight, turn, marker, license, interior) need CANBUS‑ready drivers to prevent bulb‑out messages and flicker. Front/rear turn signals often require load resistors (commonly 6‑ohm, 50‑watt) if your LEDs aren’t CANBUS‑rated.
• Headlights: For quad halogen H11/9005, choose LED kits with compact heat sinks and anti‑flicker decoders. For projector housings (9012/HIR2), use a 9012‑specific LED or a 9006/9012 cross that preserves the correct focal position; poor focus causes dark spots and glare.
• Fog lights: Replacing 9145/H10 with LEDs is straightforward; on trims with factory LED fog pods, the pod is the service part—don’t order bulbs.
• Tail lamps: Trucks with factory LED tails use integrated LED boards for stop/turn/tail. Only the reverse bulb (921) is user‑serviceable. If an LED tail function fails, the housing typically must be replaced.
• DRL behavior: Canadian trucks commonly run the 9005 high beam at reduced intensity as DRL. Many aftermarket LED high beams will flicker or strobe in DRL mode without a proper DRL/anti‑flicker module.

How to replace each bulb

• Low beam (H11 or 9012): Turn the wheel inward, remove the fender liner push‑pins for access, rotate the bulb counter‑clockwise and pull out. Avoid touching new bulb glass.
• High beam (9005): Access is similar to low beam; twist out and swap. Verify aim after replacement.
• Fog light (9145/H10): From underneath or through the wheel liner, unplug, rotate, and replace. For factory LED fog pods, remove the pod assembly via bumper screws.
• DRL: No separate bulb on most trucks; it’s a function of the high beam or park/turn. Address by replacing the corresponding bulb.
• Front turn/parking (3157A): Access the headlamp housing rear, twist the socket, and swap the dual‑filament bulb. For LEDs, observe polarity.
• Tail/brake/turn (3157 halogen tails): Lower the tailgate, remove two tail lamp screws, pull the housing straight back, twist the socket, and replace the 3157.
• Reverse (921): With the tail lamp removed, twist the lower socket and install the 921.
• License plate (194): Pry the lens from the bumper/plate light, pull the wedge bulb, and insert the new 194.
• Side markers (194/168): Front is in the headlamp corner socket; rear is in the tail lamp. Twist and replace. On LED tails, the side marker is integrated.
• Interior dome/map (578 festoon or 194): Gently pry the lens, release the spring clips for festoon bulbs, or pull the wedge bulb straight out. Use trim tools to avoid cracking the lens.

Common lighting issues for this generation

• Hyperflash and warnings after LED swaps: Caused by low current draw. Use CANBUS‑compatible LEDs or add resistors/decoders. The Ram’s PWM can also cause low‑speed flicker without anti‑flicker modules.
• Moisture in headlamps or tail lamps: Vent clogging or hairline housing cracks can fog lenses. Light condensation is normal; standing water means the housing or seals need attention. The third brake light (CHMSL) gasket is a known leak point that can drip into the cab and affect dome/map lights.
• Melted or discolored 9012/H11 connectors: Over‑wattage bulbs or poor connections create heat. Inspect and replace pigtails if brittle.
• Intermittent rear lighting: Corrosion at the trailer‑tow connector or ground points can back‑feed and dim tail/stop lamps. Clean and protect with dielectric grease.

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