Lic Plate Light LED upgrade

[///Sniper535]

I found a pair of LED bulbs that fit the connection but I get the "LIC PLATE LIGHT" out message on the CC. The bulb size says 6461, i know it's not the exact match but does that have anything to do with it or the fact that it's an LED and not a bulb?

[Tiger]

They reads the resistance... do you get the message when you turn it on before you start the car?

[///Sniper535]

when i turn on the lights

[Tiger]

Then it senses not enough current being drawn.

[bad_manners_god]

Put a 1 Ohm Resistor in the circuit...problem solved.

[///Sniper535]

on each one?

[sal_park]

on each one?

yes, kinda. Here's my take:

I assume the standard licence plate lights are 5w each and the LED ones are 1w each.

Watts
------ = Amps
Volts

Volts
----- = Resistance
Amps


for the standard lights:

5W
--- = 0.41 A
12V

12V
---- = 30 ohms
0.41A


for the LED lights:

1W
--- = 0.08 A
12V

12V
---- = 150 ohms
0.08A


So now we need to make the 150 ohms resistance LED light look like it's only got 30 ohms resistance, by as bad_manners_god said put a resistor in the circuit. After a quick calculation we can see that the resistor should have a value between 35 - 40 ohms, NOT 1 ohm !

(have a look here for more details)

The resistor needs to be in parallel with the LED light, 1 resistor per light:

hth


sal

p.s. it dosen't matter which way around the resistor goes

[sal_park]

Just done a quick google and it seems that the closest standard value is 47 ohms, available via your local maplins (or similar)

[pingu]

Good work with the sums, but I reckon that 33 ohms (which is also a standard resistor value) is probably closer to the notional 30 ohms of the 5W normal bulb.

Something to watch out for is that you'll relatively high power resistors. Normal "small" resistors can handle about 0.5 of a watt.

A 33 ohm resistor will dissipate about 5W, so you'd need a resistor rated to handle a power of a least 5W, preferably 10W so that the critter isn't on the edge of existence.

[sal_park]

fair point about the power