[Slick_FThirty]

Hello,

I have a 2013 328i and upgraded the turn signals. I specifically purchased some BA15S P21w LED bulbs for the rear.

I had the casing off with just the bulb exposed for some debugging, and I noticed that the bulbs were extremely warm. I could only touch them for a moment.
The turn signal had only been operating for about 1 minute.

Is this normal? Is this an issue or is this reasonable?

[Billfitz]

The LED itself runs cold, but the drive circuitry for it can run warm. It's why headlight LEDs have heatsinks and/or fans for cooling.

[Slick_FThirty]

Originally Posted by Billfitz

The LED itself runs cold, but the drive circuitry for it can run warm. It's why headlight LEDs have heatsinks and/or fans for cooling.

I see, thanks for explaining.

It just makes me wonder what would happen if the leds were left on for a considerable amount of time, such as hazard lights (thinking about my timing chain again).
The light unit itself is closed with no obvious dedicated cooling method.

When I got a flat tire, my hazards were on for about 4 hours. I had the halogen bulbs in at the time though.

Would the halogens be the same or worse than the LEDs? So I should not be worried?
Or is there something going on with replacing the halogen with LEDs.

The car does have LED coded....

[Billfitz]

Heat comes from current, and the current draw of LEDs, drive circuits included, is much lower than incandescent bulbs. P21w incandescent draw 21 watts/1.6 amperes, the average P21w LED draws 7 watts/0.5 amperes. The heat in the LED emanates mainly from the metal base of the bulb and the metal heat sinking, with incandescent it's from the glass surrounding the filament. If you touch the heat sink of an LED and it's warm you know it's doing its job.

[Slick_FThirty]

Originally Posted by Billfitz

Heat comes from current, and the current draw of LEDs, drive circuits included, is much lower than incandescent bulbs. P21w incandescent draw 21 watts/1.6 amperes, the average P21w LED draws 7 watts/0.5 amperes. The heat in the LED emanates mainly from the metal base of the bulb and the metal heat sinking, with incandescent it's from the glass surrounding the filament. If you touch the heat sink of an LED and it's warm you know it's doing its job.

Thanks.

I do agree with your explanation. It's just the fact that the LEDs were so hot that I could not hold on to them for more then half a second is what concerned me.

As you mentioned, LEDs are lower power than incandescent a, and so just did not expect an LED to be that hot.