The brake/taillight on the 2018 Ford Fiesta typically uses a dual-filament 3157 bulb (3157 or 3157A, depending on market). Verify by checking the bulb in your housing or consulting the owner's manual.
Bulb types and compatibility
The Fiesta’s rear tail/brake assembly is designed around a single dual-filament bulb that provides both the tail light and the brake light functions. In most regions the standard replacement is the 3157 bulb, but some markets have used variants such as 3157A or 3157K. When shopping for replacements, start with 3157 and watch for any regional suffixes to ensure a proper fit.
Common variants you may encounter
- 3157 — standard dual-filament bulb used in many 2018 Fiesta tail/brake assemblies.
- 3157A — a regional variant that is typically interchangeable with 3157 in the same socket.
- 3157K — another regional variant; verify compatibility with your specific vehicle.
In most cases, the 3157 family will be correct, but always confirm by inspecting the current bulb or checking the vehicle’s manual for your exact market.
How to replace the brake/taillight bulb
To replace the bulb, follow these steps to access the rear taillight housing and swap in a new 3157 bulb.
- Park the car, turn off the engine, and set the parking brake. Open the trunk and access the tail-light area.
- Remove any covering or trim panels that shield the tail-light assembly. Depending on the model, you may need to peel back linings or unscrew a small access panel.
- Locate the brake/taillight socket inside the housing and rotate the socket counterclockwise to release it from the assembly.
- Carefully pull the old bulb out of the socket and note its orientation for the replacement.
- Insert the new 3157 bulb into the socket, orient it as the old bulb was, and twist the socket back into place until it clicks.
- Reassemble any trim or covers, close the trunk, and test the lights (both tail and brake) to ensure proper operation.
After replacement, confirm that both the parking light and brake functions illuminate correctly and that there are no warning indicators on the dashboard.
LED replacements and cautions
If you’re considering LED replacements for the Fiesta’s tail/brake lights, keep these points in mind to avoid common issues.
- Choose 3157 LED bulbs labeled as CAN-bus compatible to minimize warning lights and flicker.
- Some LED 3157 bulbs require inline resistors or load resistors to mimic the electrical load of incandescent bulbs.
- Check fitment and clearance in the tail-light housing to ensure the LED bulb doesn’t contact other components.
Always verify compatibility with your specific vehicle configuration (trim, market, and whether the vehicle already uses LEDs in other lights). If in doubt, consult a dealership or a qualified automotive technician.
Summary
For a 2018 Ford Fiesta, the brake/taillight bulb is typically a dual-filament 3157 type, with possible regional variants such as 3157A or 3157K. Confirm the exact bulb by inspecting the current one or consulting the manual, then replace it with a matching 3157 bulb and follow proper steps to access the tail-light housing. If you opt for LEDs, choose CAN-bus compatible options and be aware of potential load-resistor needs.