Dim LED high level brake light

Question

I had my car serviced yesterday at the dealer - a number of minor issues were reported

1. Wipers are smearing - mainly due to road dirt as I had only recently replaced them
2. Water ingress in tail light - its an LED Sealed unit so not a lot I can do about that
3. Dim LED high level brake light.

My understanding is that LEDs are an all or nothing type of shot - so the circuitry itself must be ok, and rather it must be a low power (i.e. poor connection) issue.

Unfortunately I haven't had a chance to look at it in daylight so wont be able to confirm, but could there be other reasons for a brake light (specifically LED) to appear dimmer than it should?

Car is a late 2013 SEAT Leon.

Answer 1

LEDs are not all or nothing, your typical LED car light has several LEDs in it, so you can have partial failures if one or more go bad. LEDs last a very long time, however they do break early sometimes, and the circuitry is not bulletproof either, so you could have a partial failure of the unit.

The failure modes that would make sense are:

1. Some LEDs have failed: this is unlikely, one I could see, more than one would be unusual
2. LED block failure: On the LED lights I've seen the LEDs are not all on the same driver, they are usually separated in different blocks that run in parallel electrically. A failure of one of the blocks would take out all the lights on that block
3. Insufficient power: if the regulator which supplies power to the unit is sagging, that is not supplying enough power I could see the lights being dim

My money would be on #2, however #3 is easy enough to test, just disconnect the wiring harness and use a multimeter to check the voltage.