# How to test halogen and led headlights out of the car?

**URL:** <https://community.cartalk.com/t/how-to-test-halogen-and-led-headlights-out-of-the-car/158444>\
**Category:** General Discussion\
**Created:** [February 13, 2020, 6:58am UTC](https://community.cartalk.com/t/how-to-test-halogen-and-led-headlights-out-of-the-car/158444 "2020-02-13T06:58:07Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\
**Post date:** [February 18, 2020, 3:54pm UTC](https://community.cartalk.com/t/how-to-test-halogen-and-led-headlights-out-of-the-car/158444/22 "2020-02-18T15:54:12Z")

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> [@thegreendrag0n](#):
>
> were they not marketed as “never need to be replaced” ?

No different than a commercial showing a magnificent hamburger and then actually getting one 😁

Nothing lasts forever, I’m sure you know that and were being a bit tongue-in-cheek. It gets me how they have been misleading people regarding their reliability. Yes, LEDs can last orders of magnitude longer than filament bulbs but the hotter they are run, the shorter the lifespan (like anything). A 50k hour lifespan is based on the most optimum operating conditions and their expected lifespan drops off precipitously as the power goes up; the thermal loading increases or thermal cycling gets more extreme.

That being said, the LED itself is only one part of the equation. When I see _half_ the LEDs out it could be a result of series/parallel arrangement of the LEDs. Either one is dead in the series string or a connection issue with the series string. Point being, LEDs may be very reliable in of themselves but the quality of the module assembly may also be at fault.

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**Author:** ![thegreendrag0n](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/thegreendrag0n/32/9265_2.png) [@thegreendrag0n](https://community.cartalk.com/u/thegreendrag0n)\
**Post date:** [February 18, 2020, 4:04pm UTC](https://community.cartalk.com/t/how-to-test-halogen-and-led-headlights-out-of-the-car/158444/23 "2020-02-18T16:04:51Z")

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> [@TwinTurbo](#):
>
> When I see _half_ the LEDs out it could be a result of series/parallel arrangement of the LEDs. Either one is dead in the series string or a connection issue with the series string

I strongly suspect the same as I see traffic lights with whole “zones” dropping out, not individual LEDs.

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