Auxbeam B21 4257 Switchback LED Bulbs for Ford — Dual-Color 6500K White / Amber, Built-In CANBUS Resistor

Auxbeam B21 4257 switchback LED bulbs deliver bright dual-color lighting with built-in CANBUS resistors to replace 4257 sockets without hyper-flash or dashboard errors.

These Auxbeam B21 4257 bulbs are engineered for modern Ford turn-signal and parking-light sockets, combining a cool white daytime/parking mode with an amber turn-signal output. Each lamp integrates circuitry to prevent CANBUS errors and offers a high-output SMD array plus a multi-layer cooling solution for long life. The design prioritizes clear signaling, quick response, and plug-and-play installation in specified Ford models that use 4257-type sockets.

Which vehicles and sockets do these bulbs fit?

These bulbs are tailored to fit a range of Ford models that use 4257-type sockets, including front and rear turn-signal positions across select Maverick, F-150, F-250/F-350/F-450/F-550 Super Duty and similar years. Confirm your vehicle uses a 4257, 4257NA, 4257A or related variant socket before purchasing.

• Direct fit for 2022–2025 Ford Maverick front turn signals
• Compatible with 2018–2020 F-150 rear and 2021–2022 F-150 front/rear positions
• Fits 2020–2022 F-250/F-350/F-450/F-550 Super Duty rear turn signals
• Works with 2023 F-350 front turn signal sockets

How bright are these LEDs and what colors do they produce?

Each bulb uses a dense array of upgraded 3030 SMD chips to produce significantly more light than stock bulbs. In white mode they deliver a crisp 6500K appearance for parking or DRL use, and they switch instantly to a vivid 3500K amber for turn signaling.

• 28W power per bulb with a high-density SMD layout
• 6500K cool white for parking/DRL, 3500K amber for turn signals
• Fast, instant-on response—no warm-up delay
• Reportedly up to 600% brighter than many OEM filaments

Will these bulbs trigger warnings or hyper-flash on modern vehicles?

Auxbeam built these B21 4257 bulbs with an integrated CANBUS-compatible resistor/driver which prevents most error codes and hyper-flash conditions. That means in the majority of vehicles you can swap them in without adding external resistors or extra decoders.

• Integrated CANBUS driver reduces error codes and false warnings
• Designed to avoid hyper-flash on compatible control systems
• No need to prepare external resistors for most vehicles
• Includes a one-year warranty from Auxbeam

How is heat managed and what is the expected lifespan?

Long runtimes come from a layered thermal design that actively and passively sheds heat to protect LEDs and electronics. The combination of a silent fan, copper cooling ring, multiple heat sinks and an aircraft-grade aluminum body keeps temperatures lower for more durable performance.

• Four-layer cooling: silent fan, copper ring, multiple heat sinks and aluminum housing
• Built-in stable current IC to avoid radio interference
• IP68 water-resistant construction for wet environments
• Rated life expectancy up to 60,000 hours under typical use

Who is this for? The Auxbeam B21 4257 switchback bulbs suit owners of specified Ford trucks and compact trucks who want a brighter, faster-reacting turn signal and white parking light without dashboard errors. They’re aimed at DIY installers who prefer a direct-replacement, CANBUS-compatible LED with enhanced cooling and long service life. Verify socket type and vehicle year compatibility prior to purchase to ensure a plug-and-play upgrade.