Quick Info
Model
452
Estimated Cost
0€
Difficulty
Beginner
Time Required
20 Minutes
Safety Notes
Electrical Safety: Disconnect the negative battery terminal before touching any light connections to prevent short circuits.
Plastic Clips: The tail light housing can stick after years in place — use gentle, even pressure when sliding it out, never force it.
Bulb Heat: If the car has been driven recently, wait at least 30 minutes before handling bulbs — they hold heat longer than expected.
Rare Parts: The Roadster 452 tail light assembly is out of production. Handle carefully — good used units are increasingly hard to find.
Step-by-Step Guide
Introduction
The Smart Roadster 452 is now well over 20 years old, and like any car of that age, the rear lighting system is one of the first areas to show its age. Water ingress is the most common culprit — the rubber seal around the tail light housing deteriorates over time, allowing moisture to work its way into the unit. Once water gets inside, it accelerates corrosion on the bulb contacts, fogs up the lens from the inside, and in worse cases causes intermittent electrical faults that are frustratingly difficult to diagnose without removing the unit entirely. If you have noticed condensation inside your rear lights or unexplained bulb failures, a failed seal is almost certainly the reason.
The second common problem is broken bulb holders. The plastic used in the Roadster's lamp cable set becomes brittle with heat cycling over the years, and the bulb holders crack or snap when you try to twist them out for a routine bulb change. This turns what should be a two-minute job into a full wiring loom replacement. It is not a difficult repair but it does require getting underneath the car to access the connector — something most guides gloss over entirely. If your holders have already snapped, you will need Smart part number 0009518V001000000, one per side, before starting this job.
The good news is that the Roadster's tail light design is actually one of the more sensible on the car. A single Torx T20 bolt is all that holds the entire unit in place, meaning removal itself takes under five minutes once you know where to look. This guide covers everything from basic removal for a bulb swap or unit replacement, through to the full wiring loom replacement procedure — so whatever brought you here, you will find the answer below.
Locate and Remove the Single Fixing Bolt
Unlike most cars that use multiple bolts to secure tail light units, the Roadster 452 uses just one single Torx T20 bolt to hold the entire rear light assembly in place.
Locate the bolt — it is accessible without removing any trim panels. Use a T20 Torx bit to unscrew it fully and set it aside safely.
This is a small bolt so keep it somewhere it won't roll away.
Slide the Light Unit Out
With the bolt removed, the tail light housing slides directly outward away from the car body.
On older Roadsters the unit may feel stuck due to years of heat and weathering creating a bond between the unit and the bodywork. If it doesn't slide freely, a firm but gentle nudge from behind is all it needs — do not lever or pry aggressively as the housing plastic is brittle with age.
Once free, the unit will slide out cleanly.
Disconnect the Wiring Connector
With the light unit pulled outward, you will have enough slack to access the wiring connector at the rear of the housing. Press the release tab and pull the connector straight out by gripping the plastic body — never pull on the wires themselves.
The unit is now completely free from the car.
For a simple bulb swap or unit replacement, fitting is the exact reverse of these steps.
Replacing Broken Bulb Holders — Access the Connector
If your bulb holders are cracked or broken, you will need to replace the full lamp cable set (Smart part number 0009518V001000000 — one required per side). Start by removing the light unit as above and untwisting all bulb holders from the housing. Remove all bulbs and set them aside for reuse. To access the wiring connector, look through the outer hole in the bodywork — you will see the wires running to a connector deeper inside. Your arm will not fit through this hole, so access must come from underneath the car.
Replace the Wiring Loom
Jack the car up and consider removing the rear wheel on the side you are working on for better access. Looking up into the wheel arch you will be able to see the connector at the back of the light housing area. Reach in and disconnect it, or unclip the entire connector from the bodywork to give yourself more working room. Thread the new short wiring loom through the centre hole and route each bulb holder into its correct position — black holder on the outside, orange in the middle, grey on the inside. Pull the old loom out fully, plug the new loom into the connector, refit all bulbs, twist the holders back into the light unit and refit the unit to the car. Always test every bulb function before finishing.
