The rear number plate lights can be upgraded to LED however there is a problem with the bulb monitoring detecting failed bulbs and displaying a warning on the instrument cluster and MFD. There are a few approaches that can be taken and all revolve around adding extra resistance to the rear number plate light circuit to prevent the warning, one option is to install a resistor inside the car on that citcuit and the other approach is to add the resistor to the LED lights whilst being mindful that the bulbs are enclosed in a sealed enclosure so excess heat will melt the light fitting (as will fitting 10watt bulbs like the Polargs to replace the existing 5 watt bulbs).
The point at which the bulb out warning activates is around 6 watts and the LED modules that were used here are 1.5 watts so an additional 3 watts of load was required, after some testing 2 x 270 ohm resistors performed nicely and did not generate excessive heat.
Parts required are
- 2 x 1.5W T10 75 Lumen White LED Bulbs (39mm) purchased from DealExtreme for USD$10.23 delivered.
- 2 x 270 ohm 1watt resistors
Start by wrapping the resistor around the body paying attention to the end that is isolated from the body (some shrink wrap will be placed around this end to prevent a short circuit), once the legs are fully wrapped use a dremel/sandpaper/file/knife to scratch away the coating near the legs in preperation for soldering. Place some shrink wrap over the resistor and the leg on the end that is isolated and solder the legs to the end caps.
The resistor needs to be kept close to the body to maintain clearance to fit into the housing and to transfer heat to the body away from the resistor.
Once both units have been finished all that’s left is to fit them, these are polarity sensitive so if they don’t work the first time you put them in reverse them. When fitted to the holder correctly as shown below they have room to spare on each side. Make sure they are facing downwards as the light output is very directional unlike the standard bulb which outputs in all directions.