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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

Discussions

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steveastrouk

Answer 6 years ago

Ah ! Its smoking becaise it isn't designed to handle 14 W !

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fastcar123steveastrouk

Answer 6 years ago

when i had the resistor connected the led didnt light at all. should i try again with a new resistor?

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fastcar123steveastrouk

Answer 6 years ago

i think i can use 7.5 ohm 20W Wire Wound Ceramic Cement Resistors to replace the load resistors and just used the harness from the load resistors to do it. do you think that would work in place of the load resistors?

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steveastroukfastcar123

Answer 6 years ago

Another idea, out of curiosity, leave the load resistor, but remove the LEDs. Do you still get a fault ?

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fastcar123steveastrouk

Answer 6 years ago

i tried the test with 7 ohm metal clad resistors and the test failed. the bulb now wont even light up at all with the resiswotrs and i even had the bulb smoking in one scenario. im begining to think converting my lancer to 100% LEDs is impossible.

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steveastroukfastcar123

Answer 6 years ago

Then somethings wired very wrong. Did you leave the load pack in from the LED supplier as well ?

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fastcar123steveastrouk

Answer 6 years ago

if the light wont light i have tried to switch the blue and red wires (tail light and stop light) the light works perfectly fine but when the brake is applied the bulb actually gets dimmer as if on the tail light channel

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fastcar123steveastrouk

Answer 6 years ago

this is basicly what i have wired. note that it is an extension plug the plugs into the car

led tail light 2.png
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steveastroukfastcar123

Answer 6 years ago

Yes, it should do, but the resistors are supposed to be already sized for your vehicle. I don't understand why they aren't quite sufficient. Like I said before, how do the load resistors measure out ?

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fastcar123steveastrouk

Answer 6 years ago

they both measure at 20 ohms but it sounds like they should measure at 7.2 ohms becauase we figured out earlier that that would be the correct load for a 20 watt bulb. so i think if i use the 7.5 ohm resistors in place of the load resistor it will work. hopefully it wont explode again or burn out a fuse

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fastcar123steveastrouk

Answer 6 years ago

would these resistors work in place of the load resistors?
http://www.ebay.com/itm/2-Pcs-7-5-ohm-20W-Wire-Wound-Ceramic-Cement-Resistor-7R5-/280930975189?pt=LH_DefaultDomain_0&hash=item4168ca7dd5

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steveastroukfastcar123

Answer 6 years ago

yes, they'd work, but I suggest "metal clads" instead, because they're going to need to be mounted on a decent piece of metal.

Steve

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fastcar123steveastrouk

Answer 6 years ago

meaning like some sort of aluminum bracket to wrap around and screw it into the body of the car?
will i need 2 or 4?

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steveastroukfastcar123

Answer 6 years ago

Yes,

like these:

http://www.ebay.co.uk/sch/i.html?_nkw=metal%20clad%20resistor&clk_rvr_id=373888679189&adpos=1t1&MT_ID=12&crlp=12904945495_2113181&tt_encode=raw&keyword=metal+clad+resistor&geo_id=32151


You'll need 4

Steve

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fastcar123steveastrouk

Answer 6 years ago

i cant seem to find those in 7.5 ohm what ather keywords would i need to look for?

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fastcar123steveastrouk

Answer 6 years ago

this is what im going to get

http://www.ebay.com/itm/5-new-RCD-615-25W-7Ohm-1-Power-Resistor-Metal-Case-/130354008578?pt=LH_DefaultDomain_0&hash=item1e59b45202

i was able to find 7 ohm 25 watt resistors

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fastcar123steveastrouk

Answer 6 years ago

http://www.ebay.com/itm/251106742567?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649

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fastcar123steveastrouk

Answer 6 years ago

i tried that and this time the resistor had an even more violent failure by actually melting one of the wire nuts i had to secure it

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fastcar123steveastrouk

Answer 6 years ago

id also like to ad that on the driver side the led with the resistor light up however the some hook up on the passenger side doesnt. without the resistor it lights and with an incendescent bulb it lights as well. when i use the same resistor from the passenger side on the driver side it gives me the same result telling me that resistor is probably dead

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steveastrouk

6 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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lemoniesteveastrouk

Answer 6 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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steveastrouklemonie

Answer 6 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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lemoniesteveastrouk

Answer 6 years ago

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

L

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steveastrouklemonie

Answer 6 years ago

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

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lemoniesteveastrouk

Answer 6 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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fastcar123steveastrouk

Answer 6 years ago

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

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fastcar123steveastrouk

Answer 6 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

Answer 6 years ago

Oh god, one of these smart systems that goes into get you home mode when you break a bulb.

Stupid !!

OK, TWO resistors, one on the brake, one on the tail.

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fastcar123steveastrouk

Answer 6 years ago

i just tried that with a 10 ohm resistor on the brake light with the bulb plugged into the load resistor which goes on both filaments and then the LED didnt work at all and the 10 ohm resistor started smoking. surprisingly it still measure 10 ohms on a multimeter

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steveastroukfastcar123

Answer 6 years ago

So, paralleling a 10 Ohm resistor across each bulb doesn't work ?

Can you sketch what you've wired ?

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fastcar123steveastrouk

Answer 6 years ago

this is what i did when the 10 ohm resistor started smoking

led tail light 1.png
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steveastroukfastcar123

Answer 6 years ago

What is this "Load resistor" ? If its to limit the LED current, then your 10 ohms should be placed BEFORE it.

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fastcar123steveastrouk

Answer 6 years ago

it is to make the car think there is a working incendescent in place of the led

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steveastroukfastcar123

Answer 6 years ago

I know what its for, but it doesn't seem to be a low enough resistance to fool the computer. Have you measured it ?

Adding a properly rated resistor in parallel with each channel would fix the problem probably.

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steveastroukfastcar123

Answer 6 years ago

What sort of size are these resistors ? THey should be pretty darned chunky.

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fastcar123steveastrouk

Answer 6 years ago

the load resistors arepretty big in size and the 10 ohm resistor was just a small one that i would use in a small electronics project

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steveastrouk

6 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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fastcar123steveastrouk

Answer 6 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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steveastroukfastcar123

Answer 6 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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fastcar123steveastrouk

Answer 6 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