2018 Tesla Model S Bulb Sizes & Replacement Guide

As an ASE-certified master technician, I often get questions about upgrading or replacing bulbs on modern luxury electric vehicles. If you own a 2018 Tesla Model S, you are driving a vehicle that represents a significant shift in automotive lighting design. Unlike older cars that rely on traditional halogen or HID bulbs, the 2018 Model S utilizes advanced, fully integrated LED technology for nearly all of its lighting functions.

Because of this, you won't find standard bulb sizes (like H11 or 9005) for your main exterior lights. Instead, replacing a "bulb" on this vehicle usually means replacing the entire lighting assembly or specific LED modules. Below is a comprehensive guide to the lighting setup on the 2018 Tesla Model S.

Quick Reference: 2018 Tesla Model S Bulb Sizes

Note: The 2018 Tesla Model S does not use traditional replaceable halogen or HID bulbs for its primary lighting. All major exterior and interior lights are factory-sealed LED assemblies.

LED vs Halogen Upgrade Considerations

For most vehicles, this section covers CANBUS adapters, anti-flicker harnesses, and finding the right LED retrofit kit. However, because the 2018 Tesla Model S comes standard with full LED lighting from the factory, traditional "upgrades" from halogen to LED do not apply.

If you want to customize your lighting, you are generally looking at aftermarket custom headlight assemblies, upgraded LED modules for the puddle lights or footwells, or custom RGB interior lighting.

• CANBUS / Error Codes: The Tesla computer system is highly sensitive. If you install aftermarket puddle lights or interior LEDs that draw significantly different voltage than the OEM modules, the vehicle's computer may cut power to that circuit to protect it, resulting in a light that won't turn on.
• No Adapters Needed: Since you aren't retrofitting HIDs or halogens, you won't need ballast adapters, but you must ensure any aftermarket accent lighting specifies compatibility with Tesla's 12V system.

How to Replace Each Bulb (Assemblies & Modules)

Because you are dealing with integrated assemblies, replacement is generally more involved than twisting out an old glass bulb.

• Headlights (Low, High, DRL, Front Turn): If a headlight fails or the DRL burns out, the entire headlight housing must be replaced. This requires removing the front bumper fascia to access the lower mounting brackets. Be sure to disconnect the 12V battery and the high-voltage loop before doing major electrical work.
• Tail Lights, Brake, and Rear Turn Signals: These are also sealed units. They are accessed by removing the interior trunk lining. There are a few securing nuts and a single electrical connector holding the outer and inner tail light housings in place.
• Fog Lights: Fog lights are mounted in the lower bumper fascia. Similar to the headlights, replacing them usually requires removing or partially dropping the front bumper to access the mounting hardware.
• Interior & Puddle Lights: These are the easiest to service. The door puddle lights and footwell lights are small rectangular LED modules that can be gently pried out with a plastic trim tool. Simply unplug the connector and snap a new OEM or aftermarket module into place.

Common Lighting Issues for this Generation

While LED lights are designed to last the lifetime of the vehicle, the 2018 Model S is known for a few specific lighting faults:

1. Yellowing or Burnt-out DRLs: This is arguably the most common lighting issue on this generation of the Model S. The LED signature strip (the daytime running light) is prone to overheating, which burns the acrylic light guide. This results in a distinct yellowing or partial failure of the DRL strip. Unfortunately, the only factory fix is replacing the entire headlight assembly.
2. Tail Light Condensation: The seals on the rear tail light assemblies can sometimes degrade or vent improperly, leading to heavy condensation inside the lens. While a little fog is normal in specific weather, pooling water will eventually short out the LED board, necessitating a replacement.
3. Firmware Glitches: Because the lights are controlled by the vehicle's centralized computer modules, occasionally a software update or glitch can cause the headlights or interior lights to behave erratically. A simple scroll-wheel reboot of the MCU often resolves these temporary software-induced lighting quirks.

Working on a highly computerized EV can be intimidating, especially when bumper removal is required just to fix a failed headlight LED. If you are experiencing DRL yellowing, tail light condensation, or need an assembly replaced, don't hesitate to seek professional help. Find a trusted shop on Repairius.