Trucklite Tail light and front blinker longevity?

[tim292stro]

The heat won't melt the epoxy until it burns the plastic, FR4 circuit board and melts all of the solder. Those look like red piranha-style LEDs, good news there is that they are CHEAP (in all senses of the word unfortunately).

One good thing is that optical epoxy is REPAIRABLE - in other words, cut it out and when you pour new epoxy in there to seal it the new epoxy will fill the voids in your cuts and make it look almost like new. The bad news is the construction of the fixture itself I'll bet they are ultrasonically welded together after epoxy potting - in this process, the two halves are held together under pressure and one side is attached to an ultrasonic transducer which vibrates the one half until the plastic edges in contact heat up and melt together. This is what I being done with modern plastic headlights and complex tail light fixtures.

The other downer I see is that in addition to the cheap through-hole LEDs and resistors, I don't see any TVS diodes or voltage regulation on the Printed Circuit Board (PCB). I'm guessing they crammed that stuff in the bump on the back where the cables come out. You can see though in your pictures that the LEDS for the tail light seem to be in 3-LED series strings, with one current limiting resistor for each series string, this means they (Trucklite) designed the LED PCB for about 6Volts (each LED is about 2V-fwd), and use regulation to step down the voltage to the string voltage.

This also suggests that the LEDs are probably fine, and it's the step-down regulation in the back of the fixture that is bad - and may mean that you can salvage some without affecting the outward appearance of the fixture (i.e.: you can cut out and replace the regulator assembly with a new one). Try cutting off the back of the one you already cut open, and see of you can carve out the regulation circuits. Do you (or your friend) have a bench power supply? I'd offer to help fix these but I just don't have the time (sorry), but I'm willing to arm-chair it .

[Edit:] I would have built these differently, I would have used a flexible circuit board, so that vibration wouldn't slowly crack the PCB and make the lights flicker. Also, if it turns out they never put in TVS diodes on the input wires, that will allow spikes to slowly (or very quickly) burn out the regulator - which I'm guessing was only rated for 30-34VDC (in 12VDC electrical systems it is common to find 50V rates parts due to spikes, so for 24VDC I'd expect to see 80-100V rated parts). [/Edit]

 

[welldigger]

Yes we have a variable 0-36v dc power supply to do bench testing. The big issue is the expoxy encases everything from the tips of the leds back. Its about 1 3/4" thick. You can see through a window in the first layer that there is at least 2 layers (possibly 3) of circuitry. The epoxy is bonded to the circuit board and housing. Its like they set the assembled components inside the back half of the housing then filled it with liquid epoxy. I also agree that they sonic welded the top half (the lens) to the other half. Again, for a repair to be successful the first step must be softening and then removing the potting material.

 

[Hainebd]

How about a solvent to soften dissolve the epoxy. Xylene may do it and may not distroy electronics.

 

[quickfarms]

Ethanol in gasoline is reported to slowly dissolve fiberglass fuel tanks in boats

 

[welldigger]

Somehow I feel that dunking a tail light into a bucket of gas or some other solvent will only make things worse. That being said keep the ideas coming. If we keep trying maybe we can eventually come up with something.

 

[tim292stro]

Try using dental picks wired to the bench power supply to pierce the potting compound before digging into it If it turns out to be on the back (regulators), it would save you some time figuring out which part of the potting compound you want to remove.

 

[welldigger]

That may could work. After doing some reading I have come to the conclusion that heat is my only option. I know for a fact trucklite uses a hard epoxy to pot these fixtures. This stuff is almost impervious to most solvents. The solvents that will dissolve it are extraordinarily difficult to come by and the have 2 major side effects. One, not only will they dissolve the epoxy but also the circuit board. Two, they tend to carry things directly through the skin into the blood stream. Very nasty stuff.

So now the next big question. How much heat is required to soften it and how to direct the heat in a way that won't melt or fry other components?

 

[ATPTac]

Well this thread is disheartening, I was wanting to convert all my exterior lamps to LED. If they're not going to last very long, then I don't see it being worth the money... Did you ever figure out what caused them to go bad? Was it definitely bad grounds? If that ends up being the case then I might still look into getting them and just run ground wires back up to a negative on one of the batteries.

 

[welldigger]

I only suspect it was bad grounds. Not positive. Mine were grounded to the frame. Thats why I preach running a ground to the battery. It helos rule that out as a possibility.

 

[ATPTac]

I'm curious to see if anybody else can weigh in that has had them installed on their truck for a decent amount of time. I know LED technology has come a very long way in the past few years, I wonder if Trucklite updates their hardware when newer/better technology comes available.

 

[PETE BALLARD]

this is their warranty page from their catalog..........

https://www.truck-lite.com/webapp/w...alog/warrantyinfo.jsp&storeid=10001&langid=-1

according to the page linked above it only covers the original purchaser

 

[gimpyrobb]

So now the next big question. How much heat is required to soften it and how to direct the heat in a way that won't melt or fry other components?

Section the one you have taken pics of. Once a day, put a piece into the oven at different temps. Thats the best way to find out, or join some injuneering forums and ask them...

 

[welldigger]

Well if you wanna find it in my local landfill go right ahead lol. It was a royal pita the cut the first one open. Honestly, after researching on every electronics forum I could find, I'm just not motivated to try. I could easily spend hours pecking away at the potting compound when I could just as easily get led bulbs for my regular light housings and move on to other projects. Even if I did figure out how to fix them the time involved would make the cost prohibitive. I think I could build an led circuit superior to the trucklite circuit. (Given enough time and motivation that I don't have to work on this).

 

[tim292stro]

You'll start to hurt the diodes at anything sustained (longer than a few minutes) over 350F, however, you will start to melt the plastic casing before then. The solder holding the parts to the board should melt in the 240F range.

Well this thread is disheartening, I was wanting to convert all my exterior lamps to LED. If they're not going to last very long, then I don't see it being worth the money... Did you ever figure out what caused them to go bad? Was it definitely bad grounds? If that ends up being the case then I might still look into getting them and just run ground wires back up to a negative on one of the batteries.

LEDs #1 killer is heat. Running LEDs creates heat at the die (the little piece of silicon that makes the light), the leads that attach the diode to the board take away this heat (and in high-power LEDs thay have a dedicated heatsink pad or plate). If the ambient temperature is too high, not enough of the heat will be taken away. The two biggest killers after heat, is over-current, and over-voltage - which leads to over-current. Both of those actually lead to the #1 killer heat.

Outside of the LED itself, there are other things to contend with:

• Mechanical vibration leading to Printed Circuit Board failure - there is a 2-6mil layer of copper on the board, think of this like a piece of scotch tape on a piece of wood... If you bend the wood, eventually the tape will rip and there will be to separate pieces of tape. Bend the wood further, and the whole piece of wood will break. Same thing with the copper/board - it can crack and make an intermittent "open circuit", which would have the strobing effect that an above poster mentioned every time the vibration makes to the two pieces of copper touch and separate.
• Regulation failure - the components that provide a usable power to the LED can also fail in a number of ways, a power surge can take out a regulator or capacitor, a resistor can literally burn up from a short, and components can rust inside a housing.
• Power leads torn out, or cold solder joint - where the wires connect to the PCB or regulator circuitry is very susceptible to vibration and poor workmanship. The wire can pull out of the circuit board and create an open circuit that is only 1/64" or less, but completely breaks the circuit. If this happens on a ground lead, it will kill the whole fixture. If someone was dangling the fixture from the wires while they were putting in is or taking it out this could do it. A cold solder joint is made when either the joint temperature wasn't high enough for the molecular bond between the solder, wire, and circuit board to take place - or it can be as simple as not cleaning your surfaces before soldering which creates a film that the solder won't bind to.

Potting usually takes care of the vibration issue, but given where these are mounted and what they are mounted to, I reiterate my position that I would have done a flexible circuit board instead of rigid - that would make the connection last as long as the mechanical capabilities of the copper, not tensile strength versus fiberglass (pretty sure copper is weaker there).

Over-design and clamping (ESD/surge supression) the voltage regulation will make it last longer but adds cost and complexity (not likely to be done with these).


I'd say if you can find LED fixture run with them, but make sure you get them from an SS Member, NOS, or as a last resort eplace - since you shouldn't pay retail (the government doesn't why should you?). And be carefull when you put them in, many are ESD sensitive (I noticed the Grote tail-lights I bought came in anti-static bags), don't hang them from the wires, and make sure you have a good clean ground to the chassis (a little conductive grease in the connectors doesn't hurt either).

 

[PETE BALLARD]

section the one you have taken pics of. Once a day, put a piece into the oven at different temps. Thats the best way to find out, or join some injuneering forums and ask them...

i wish you would bring back your old avatar, for the life of me after seeing it i must ask what are we talking about? Oh to be one of santa's helpers! The wild and crazy headlight nuts usually bake the headlights 10 minutes @ 270 degrees f to separate lenses from the housings. Don't forget to use welding gloves not the wife's oven mits. Time may be slightly more or less based on unit size

 

[rustystud]

At the metro transit where I work we have had terrible results using "TruckLite" LED's . Mostly it is vibration that kills them, with water intrusion being the second reason. We had tried many different mounts and they finally went with a different manufacturer. LED's are cool and very bright ! but for the cost and longevity that they get, I won't go with them. At work now we will replace them about every year, even though they are suppose to have a ten year life.