Remove the headlight from the car following this guide.
Warm up the clips before attempting to unclip them as they can snap very easily.
I used a standard fan heater but a hair dryer will work just as well.
Don't allow the clear lens to get too hot or it may melt.
Once all the clips are undone, the clear lens will easily pull away from the back.
Hold the front part of the reflector and pull it towards you to unclip it from the light.
If you think you know it all and ignored the headlight removal guide above and for some reason
you can't get the front reflector out, remove the indicator bulb holder. Read everything in future.
Look on the back and you will see two tabs, push these in and the diffuser will come out.
This leaves the main reflector which is still covering the wiring and self level unit.
Use a 6mm allen key to wind both adjusters anticlockwise to raise the reflector.
A gap will appear underneath the reflector, you will see a white clip near the back.
Place a long thin flat blade screwdriver in the front of the light and flip the clip up.
Pull the reflector away from that clip, turn both adjusters clockwise until the reflector comes out.
On a few smarts, it has been known for the adjuster to disconnect itself.
This can cause a lack of movement when using the in-cabin light adjustment toggle.
Behind it you will find a small wiring loom and the light level adjuster. Remove the screws.
Pull the wiring connector from the levelling unit.
The main wiring connector has three clips, one large and 2 small.
Using what ever you can find, push ala the clips in at once and slide the connector out.
I used a hacksaw blade end and two small allen keys. It is tricky so keep trying.
Here is the wiring loom. The connectors, starting from top to bottom are...
Side light bulb holder, H1 bulb connector, H7 bulb connector, main connector, levelling unit.
Levelling Unit Replacement
The levelling units have been known to become faulty causing a buzzing noise and not much
movement. Smart don't sell this part separately but we received an email from Ronald W saying
that you can also use a leveling unit (1U0941295A or 1J0941295A) from Volkswagen.