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2020 Ascent Touring
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1,125 Posts
Discussion Starter · #1 ·
Am I missing something? To me, the point of the auto industry's LED changeover was to lighten vehicles and consequently improve fuel efficiency (lighter guage wiring, smaller batteries and alternators).

Everything I've read about changing OEM traditional bulbs with LEDs requires adding back resistors to mimic the OEM bulb's load.

If you're not cutting electric consumption you're not cutting load on the alternator so no fuel savings.

What's the end game for LED replacements?
 

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2020 Ascent Limited
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101 Posts
I think the sticking point is the safety standard that requires the car to "know" when a turn signal bulb is out. I think all interior lights can change over just fine and may actually reduce the load on the alternator. But, resistors are required for the more advanced turn signal indicator circuit.

When an incandescent bulb blows out, that changes the load on the system and it is "smart" enough to react by making the system blink faster ... to indicate to the driver a turn signal bulb is out. LEDs don't behave this way. Many times you throw an LED in a turn signal, it will simply blink quickly as the system thinks there is no bulb at all because the draw on the LED is so minimal. Hence the resistor.

There might already be technology to do this with LEDs, but any car that has traditional turn signal bulbs will face this.

Requirement states: S5.5.6Each vehicle equipped with a turn signal operating unit shall also have an illuminated pilot indicator. Failure of one or more turn signal lamps to operate shall be indicated in accordance with SAE Standard J588e, Turn Signal Lamps, September 1970, except when a variable-load turn signal flasher is used on a truck, bus, or multipurpose passenger vehicle 80 or more inches in overall width, on a truck that is capable of accommodating a slide-in camper, or on any vehicle equipped to tow trailers. (Federal Regulation)
 

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Registered
2020 Ascent Touring
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1,125 Posts
Discussion Starter · #3 ·
I think the sticking point is the safety standard that requires the car to "know" when a turn signal bulb is out. I think all interior lights can change over just fine and may actually reduce the load on the alternator. But, resistors are required for the more advanced turn signal indicator circuit.

When an incandescent bulb blows out, that changes the load on the system and it is "smart" enough to react by making the system blink faster ... to indicate to the driver a turn signal bulb is out. LEDs don't behave this way. Many times you throw an LED in a turn signal, it will simply blink quickly as the system thinks there is no bulb at all because the draw on the LED is so minimal. Hence the resistor.

There might already be technology to do this with LEDs, but any car that has traditional turn signal bulbs will face this.

Requirement states: S5.5.6Each vehicle equipped with a turn signal operating unit shall also have an illuminated pilot indicator. Failure of one or more turn signal lamps to operate shall be indicated in accordance with SAE Standard J588e, Turn Signal Lamps, September 1970, except when a variable-load turn signal flasher is used on a truck, bus, or multipurpose passenger vehicle 80 or more inches in overall width, on a truck that is capable of accommodating a slide-in camper, or on any vehicle equipped to tow trailers. (Federal Regulation)
Didn't know that.

Other makes include LEDs in their highest trims, in 19-20, only touring got LED but only for headlights. Would have been nice to have the full LED upgrade including the interior. The incandescent bulbs in the map and tailgate are pretty pathetic.
 

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2,449 Posts
You get the benefit of a brighter bulb with instant on-off instead of fading in and out.
Yes, with the resistors you’re not really saving energy. It could be pitched as safety related as I stated above but it’s mostly aesthetic.
Many new vehicles are coming with led turn signals and bulbs, but they’re also coming with multiple or string leds vs a single bulb. Energy savings is definitely debatable...
 
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