Hi.
The Fiat canbus system is far more sensitive than the one in my old Rover 75 and the error free LED's that worked OK in the 75 cause the triangle to light up and a "check number plate light" to come on, I've paralleled a 75 ohm across each bulb to no effect so in all I have 37.5 ohms in the circuit plus the already error free bulbs.
Before I lower the value any further has anyone fitted a suitable resistor to clear the error message?
To replicate the filament bulbs (when hot) I'd need to go as low as 15 ohms of at least 10 watts, so a fairly hefty resistor, if the canbus doesn't show one filament bulb out then my 37.5 ohms isn't that far out.

Hi.
With 30 ohms across the feed the warning goes out and non canbus LED's will work fine.
I'm going to order one of these, ( http://www.ebay.co.uk/itm/WELWYN-WH...128451?hash=item4d520df603:g:CasAAOSwopRYdkwE )
and mount it with heat conductive epoxy on the inside of the tailgate on the lower flange. It's rated at 10 watts but only dissipating 5.3 watts at 12v.

This makes me smile. The reason for using LED bulbs is that they draw less current (or, technically, are more energy efficient). That benefit is lost if you then have to add back resistors to draw the same total wattage that the filament bulb did in the first place. Note also that the number plate lights are supposed to be 'dim' - hence why they only use 5W filament bulbs. Many LEDs alternatives are too bright and result in a car showing a white light to the rear, rather than just lighting the number plate. This is A Bad Thing. (not looking for a 'debate' on this...)

Hi.
Don't get me wrong I do understand your reasoning. I got pulled for having defective number plate lights about three years ago, they were 5w festoons and the window was clear. TBH I fully understood the traffic cops reasoning and when he saw they were functioning OK and clean he said Oh well you didn't design the car and actually apologised for wasting my time.

If you look at my calcs the 27 ohm resistor is drawing about half the current of the two original bulbs, each LED lamp does produce more lumens than the original festoon and is a lot cooler, on my 2014 car there is already some deformation in the plastics due to the heat produced by the standard bulb. Moving the 5 watts of heat to a better area in my view is a bonus.
Each to their own though.