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I recently was gifted some LED brake lights for my car, but I was told by someone at the auto store I may need a resistor before I remove the OEM bulbs. Any idea if there's truth to that? Driving a Ford Focus SE, 2013, Sedan, FFV DOHC version.
 

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https://www.focusfanatics.com/forum/mk3-focus/322721-canbus-leds-do-they-work-not-work.html

With the LED lamps, they are too high resistance, so the system will probably report that you have lamps burned out. The solution seems to be to splice in a resistor, so that the system sees the expected resistance/current on the circuit, and it does not trigger the "lamp out" warning on the dash.

It's important to note that once you splice in the resistor, the lamp out warning will not trigger, even if the lamp really does burn out. Also, the way that "CAN bus error free" LEDs are made means that they will also not trigger the lamp out warning, even if they do burn out/fail. The will also use the same amount of power/current as the incandescent lamps do, as well as produce the same amount of heat. (That's what the resistor is for, to shunt the additional power/current needed to prevent the system from reporting a failure.)
 
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Well, the brake lights are separate from the turn signal lights. The brake lights don't need resistors, only the turn signals to prevent hyperflashing which on your dash is a very fast rapid flash (which normally tells you your bulb is out).

On the turn signal, a resistor is spliced in with one end on the power wire and the other on the ground wire.
 

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You won't get hyper flash is correct but you'll get a warning light on the dash like Supra said if you don't put resisters in. At least on most newer cars. Everything will function properly so theoretically you can run it light that but it's very annoying having that message on all the time.
 

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Discussion Starter #5
Thanks guys. I decided it wasn't worth the troubles. I'm just gonna buy extras of OEM bulbs and keep them in the car until they go out.
 

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Thanks guys. I decided it wasn't worth the troubles. I'm just gonna buy extras of OEM bulbs and keep them in the car until they go out.
It'll take years before they go out... we have mandatory rear ON lights at night here in Canada. Remember that 4 months of the year, it's dark at 4PM here. My car is 6 ½ years old and they are still running.
 

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It'll take years before they go out... we have mandatory rear ON lights at night here in Canada. Remember that 4 months of the year, it's dark at 4PM here. My car is 6 ½ years old and they are still running.
I do like canada's requirement of mandatory DRLs on cars. It makes sense from a safety standpoint. It just sucks when people don't realize DRLs aren't the normal night-time driving lamps.
 
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