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when switching a car over to LEDs would it be possible to place a resistor acrross the led? Answered

i bought led tail bulbs and led load resistors for my car but when i have the load resistors in place the brake light stays on constantly and there is very little current going throught the LED bulb. how can i fix this problem without needing to go buy new led bulbs or new load resistors. the resistors i have are plug and play so the wireing could be changed if needed. i thought about placeing a 1Mohm resistor across the negative and positive leads of the led bulb but i didnt know if that would be acceptable

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steveastrouk
steveastrouk

8 years ago

It needs a bigger resistor than a 1M. What wattage have you replaced ? The flash rate on old lamps was determined by the bulb resistance. If you had 20W brake lights, you need a 12^2/20 Ohm to "replace" it.

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lemonie
lemonie

Answer 8 years ago

Do I understand that the "wink-device" is still a bimetallic-thermal thing? So although you use less energy on light you still need to run a heater?

L

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steveastrouk
steveastrouk

Answer 8 years ago

Not from the sound of it here- this thing has an ECU which is getting up set by the low loads of the LEDs.

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lemonie
lemonie

Answer 8 years ago

So you need to put load on it and waste energy through a resistor?

L

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steveastrouk
steveastrouk

Answer 8 years ago

Yep. Stupid innit ? If the system was designed for LEDs, it wouldn't be necessary.

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lemonie
lemonie

Answer 8 years ago

I was lying in bed this morning and heard this loud-band, followed by a bit of a tyre-squeak.
About 1-2 hours later when I went for the bus (stopped waiting for the road to be cleared) - I did see a completely-intact orange-glazed indicator-bulb in the gutter. I would have picked it up, but the multitude of Police may have objected.
Seeing the two vehicles, I reasoned that one driver failed to spot the other and the tyre-squeak came from one of them bouncing-backwards.

L

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fastcar123
fastcar123

Answer 8 years ago

the load resistors i bought measure at 20 ohms if that helps any

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fastcar123
fastcar123

Answer 8 years ago

so i would need a 7.2 Mohm resistor across the positive and negative leads of the bulb? would that work?
so in the case of load resistors the load is set too high?

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steveastrouk
steveastrouk

8 years ago

144/20 = 7.2 Ohm.

By all means, try your 20Ohms, the lights SHOULD flash, but I don't guarantee it.

Ideally, you'd need an electronic flasher relay.

Steve

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fastcar123
fastcar123

Answer 8 years ago

well actually im not useing the leds for turn signals im usuing them for tail/stop lights only. the turn signal is a differant bulb

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steveastrouk
steveastrouk

Answer 8 years ago

Sorry, my fault for misreading there.

Are you sure you haven't broken a wire to the lamp cluster ? Broken grounds around there play havoc with logic and lamps.

Have you put the load resistors across the LEDS ?

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fastcar123
fastcar123

Answer 8 years ago

im certain ground isnt broken because the old uincendesents still work fine and ive place the load resistor across the led but thatrs when it makes the brake light stay on constantly. im wordering if placing a resistor on the leads of the load resistor would help

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steveastrouk
steveastrouk

Answer 8 years ago

WHat happens if you DON'T fit the resistor ?

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fastcar123
fastcar123

Answer 8 years ago

the led works perfectly fine and it has no problem with the brake light. however my dashoard computer tells me to service engine soon, and there is a significant engine power loss

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fastcar123
fastcar123

Answer 8 years ago

should i place a 7.5 ohm resistor across the negative and positive leads of the load resistor and put it and the led bulb in the car?