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Electrical guides and mods

Licence Plate Lights

Replacing the numberplate lights with LEDs is not a common mod in the smart fraternity but is very common with the VW owners.

Modification Details

The light given out by standard 12 volt low wattage filament bulbs will always be
poor, the output glows yellow and is very tiring to the eyes. Not to mention it blends
in with all the other lights on all the other cars on all the other roads. These guides
can also be used to fit a replacement bulb instead of an LED.


Here is the typical view of the back of a smart car. The standard bulbs are C5W (39mm) or 239.

It's a dim and dingy sight that can be rectified very easily and with great effect.
Not only do LED numberplate lights look better they also make the car stand out more.
This reduces the risk of someone going into the back of you.
The pure LED colours, crispness and brightness is very hard too ignore.

Fitting the lights

The light holders cannot be accessed very easily from the outside, it's easier to remove the boot panel and unclip them from the inside. The clip (circled in red) are prone to snapping.

The bulb is held in by two spring contacts and the replacement bulbs should
be 36mm - 39mm in length, push them in place and angle them towards the
diffuser. Test they both work before refitting the holders into the panel.

I started using the smaller festoon shown above but one started flashing after about 3 months.
I am hoping the larger one with the bigger LEDs will work better.
These 9 LED 39mm festoon lights were bought from Ebay.

As you can see, the light is much crisper and obvious..

The Clip Broke And Now It Just Dangles

Same here and i'm glad that it did, I drilled a small hole into the far edge of the diffuser
and screwed the bulb holder back into the boot panel. The finished article looks no
different to before except it is now a lot easier to access to change the bulbs.

Next time, I will purposely snap the other clip off and use this fix.

Large PCB Festoon Lights

Although the 39mm was a good length, the width was just too much to fit in the housing unaltered. Luckily the fix is easy, just cut a section out of each side and it fits.


The standard bulbs are W5W or 501, these can also be purchased in LED form.

Chances are the licence plate bulb holders are loose in the holes, it's very common.
If not you can either pull them towards you and lift the back or side something under the front.

The bulb holder will now pop out.

Twist the holder a quarter turn anticlockwise...

...and the bulb will slide out in the holder.

Replace the bulb and test. If you are fitting an LED replacement it will only work one way round.
If it fails to illuminate, remove the bulb, turn it 180 degrees and refit.

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