Auxito LED’s

[Pklee28]

Ok, so I have an XLT Tremor. Bought Auxito cargo and license plate lights about a month ago. Worked great. Bought and installed high beams, low beams, and fog lights this weekend. Again, worked great. The next day, I noticed the cargo light on the passenger side was blinking very fast. Sometimes it would even not come on at all. The NEXT morning I noticed the license plate light on the passenger side was dim and blinking too. Intermittent and sometimes they both even work fine. Has anyone come across anything like this? It seems like installing the headlights caused an issue. Especially with both lights malfunctioning on the same side of the truck. I haven’t swapped the bulbs to check yet, but what’s the deal?

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[JDowns]

I doubt its the headlights. Completely different circuits. What you are describing is most likely thermal runaway.

Running LED's from a constant voltage can lead to thermal runaway. As the forward voltage decreases the temperature increases, or in semi technical terms the resistance decreases with temperature creating a scenario where the LED will draw more and more current (heat) until it shuts down. This can lead to blinking until failure. This is also why an LED circuit will work just fine in colder weather and all of a sudden fail when atmospheric temperatures rise.

LED's should be driven with a constant current driver to alleviate these issues. This is a reason why drop in LED's really should not be used on circuits designed for halogen bulbs without the use of a constant current driver. Some drop in solutions will provide this internally or offer external solutions. You may get mixed results from LED to LED, manufacturer to manufacturer, and location to location without the use of a constant current driver.

For example if you look at a reliable manufacturer like Diode Dynamics, in the description of all their drop in LED solutions.

Reliability. Diode Dynamics LEDs are built with constant-current inductive circuitry, along with transient suppression.

Installing LED's without a constant current driver is a recipe for problems.

 

[MountainGoat]

I doubt its the headlights. Completely different circuits. What you are describing is most likely thermal runaway.

Running LED's from a constant voltage can lead to thermal runaway. As the forward voltage decreases the temperature increases, or in semi technical terms the resistance decreases with temperature creating a scenario where the LED will draw more and more current (heat) until it shuts down. This can lead to blinking until failure. This is also why an LED circuit will work just fine in colder weather and all of a sudden fail when atmospheric temperatures rise.

LED's should be driven with a constant current driver to alleviate these issues. This is a reason why drop in LED's really should not be used on circuits designed for halogen bulbs without the use of a constant current driver. Some drop in solutions will provide this internally or offer external solutions. You may get mixed results from LED to LED, manufacturer to manufacturer, and location to location without the use of a constant current driver.

For example if you look at a reliable manufacturer like Diode Dynamics, in the description of all their drop in LED solutions.

Reliability. Diode Dynamics LEDs are built with constant-current inductive circuitry, along with transient suppression.

Installing LED's without a constant current driver is a recipe for problems.

Interesting. I installed Auxitos but found it odd leds would have little fans in them. I guess that's a band aid?

 

[Trigganometry]

Interesting. I installed Auxitos but found it odd leds would have little fans in them. I guess that's a band aid?

Fans are necessary to keep air moving by the heat sinks. If they’re in an enclosed space you technically have a mini oven. As mentioned by OP the thermal runaway will happen at some point as they can’t cool properly.

 

[MountainGoat]

Fans are necessary to keep air moving by the heat sinks. If they’re in an enclosed space you technically have a mini oven. As mentioned by OP the thermal runaway will happen at some point as they can’t cool properly.

Well I guess I'll see. I don't do much night driving but it wouldn't be good if they all went out at once! I did low/high and fog. I'm going to put my old halogens in the glovebox just in case.

 

[JDowns]

Well I guess I'll see. I don't do much night driving but it wouldn't be good if they all went out at once! I did low/high and fog. I'm going to put my old halogens in the glovebox just in case.

It's always a good idea to keep a backup in the vehicle for critical bulbs like headlights. Cheap insurance if you will.

As @Trigganometry mentioned the fans are there to aid in cooling the heatsink. Not every design requires a fan, but in this case due to the size of the heatsink most likely not meeting the cooling requirement alone (space constraints), a fan is introduced to aid in cooling. I wouldn't be overly concerned about thermal runaway on the headlights as the specs do mention an IC circuit, for whatever thats worth as they do not specifically mention constant current driver. But the failure rate would be way to high in my opinion if they did not include a constant current driver, so I would assume their marketing language of IC circuit to interpret as a constant current driver.

If I test a 4 chip drop in like below that has a wide operating voltage, 5VDC - 18VDC, no constant current driver, but a heatsink. The current draw is very stable (0.202 - 0.210), but in about 5 minutes the heatsink becomes too hot to touch, but remains stable. Without the heatsink it becomes hot enough in those five minutes that the chips desolder themselves at close to three amps, and the light output is dim and flickers.

As you can see these are low amp draw LED's when designed properly. But put these on a 5amp circuit, and there is not enough fuse room for any sort of protection against thermal runaway (no heatsink) before temperatures become very unsafe. To desolder those chips, those temps would be north of 300F.

A low cost 350mA constant current driver like a 7027-D-350 would have saved the day in this instance. The heatsink is needed to maintain temperature stability and LED longevity, but not having a constant current driver as protection is a terrible idea IMO.

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