hi

i'm fitting some R1 lights (LED) to my mk and i have a bit of a blonde moment and well to cut a long story short. the light has ground, tail and brake wires (black, yellow and blue) and the tail has 2 12 ohm resistors in series in the wire. well i cut these out (run over them when putting car on a trailor) . i connected the light to a battery without the resistors in line and they seemed to work the tial lights are not as bright as the brake lights which seems ok. but my question is why are the resistor needed????

cheers steve

They're current limiting. LEDs will work without them, just not for long....

and if you have clear lenses the colours will change from whatever they should be to red then stop lighting

A circuit diagram would be better than your description - can't say I fully follow it.

LEDs require current limit resistor but 12 ohm is far too low a value for a single LED conected to 12 V. There may be several LEDs connected in series, like I said, circuit diagram.

So my guess is that the resistors are there so that the rear and brake lamps used the same LEDS. The resistors are by passed when the brake pedal is pressed, so the LEDs are brigher due to more current in them.

if the resisitors are in series then they are voltage limiting, if they were in parralel they would be current limiting.

if you cut out the resistors the led's life can me measured in seconds...minutes at most......leave them in.

ive just realised what is going on with those resistors-
LED's are quite parculiar in that they are not a resistive load, they will eat whatever current you put into them so that would explain it if the resistor was parralel.
but in series? posibly because the LED doesnt have the same presence as a normal lamp therefore will make a flasher relay behave abnormally? so the resisitor takes place of a lamp to give enough resistance for the relay to flash at the correct rate.

Russ.

a resistor in parallel will increase current in the circuit, in series it will reduce it. you need more current to operate the relay on the indicators than the leds can draw thats why a parrallel resistor is fitted, much better to fit an led relay than mess about putting extra resistors in
keith