LED Brake Light $350 repair

Thanks for posting about your problem. The diode likely protects against polarity reversal while the resistors provide a current limiting function for the LEDs within the brake light.

Please take photos of the disassembled light assembly and let us know what the failed component was, when you figure that out.

 

jstack,

Although I've had both my tail light assemblies out, I didn't go digging
around to see what the brake light wiring looked like. It sounds pretty
bizarre.

Putting aside for a moment that the arrangement is not what you'd
expected, from what you see, can you think of any reason why that was
the preferred way to assemble it? Maybe assembly in a "special needs"
work site, or an especially low tech environment, like ... what?

After all, it should be easy to quality test the LED assembly before it gets
put in the tail light assembly and closed up tight.

 

This is typical of many if not most new electronics designs. The LED brake lights are not replaceable because they are not likely to fail. The way it is built in the Prius is less expensive overall for Prius owners, but more expensive for the rare unlucky ones like you. Total cost of ownership is lowered and reliability is increased, but unfortunately when you do have a problem it costs more to repair.

We have been doing this for years in the electronics industry. Are you old enough to remember TV sets with vacuum tubes (other than the CRT)? All of the vacuum tubes were socketed for easy replacement, which was a good thing since they had to be replaced on a routine basis. Early transistor designs used sockets for the transistors. It didn't take long to realize that the socket was more likely to fail than the transistor. Now you never see sockets for transistors or ICs except in very special cases (CPUs and such). A transistor or IC almost never fails. When one does, you usually end up replacing the entire board.

Tom

 

12v directly to the LED or the brake light housing? 12v directly to an LED will make it fire up.. then go dim... forever...

i wonder if something failed and maybe they did burn out. too much power for some reason... shrug

have you checked all the soldering? it is all solid?

 

An LED needs ~2V. If you applied 12V across each LED then you probably destroyed them. This is why a resistor is in series with each LED - to limit current.

Since you have a 12VDC source, I would have suggested that you apply this to the brake wire (positive side) and ground wire (negative side), then use a voltmeter to trace how the voltage flows through the resistors and LEDs, to see where voltage no longer is available.

 

If all the LEDs are dim, it's probably not a single LED or resistor failure. I would suspect a bad common ground, or a bad diode.

 

Hi All,

Looking at Jstack's "brake light LED control board" it seems there are five 24 ohm resistors in seiries that are just across the 12 V. 24 times 5 is 120 ohms, so I guess the goal was to have a minimum of .1 amp flow, in case the LED string failed. Because the other four resistors (7.5 ohms) look to be the voltage droping resistors for a series LED string. You can tell this as it has the diode in series with this string or resistors. Presumably the diode is there to limit reverse current and protect the complicated LED assembly should the wires be hooked up in reverse. Its not really a control board. Its a balast board.

The string of 24 Ohm resistors might be a defogging heat source for cold weather operation. Which would explain the lower mounting position.

Yea, they should not have wired everything in series, even if it may save money (fewer wires and contacts in the connectors) or energy, on this. This makes it prone to failure of course. Its the classic Christmas Tree Light problem. One failed component neccesitates replacement of the whole assembly. Rather than an acceptable 5 brake LEDs, instead of 6.

Ok. 6 RED LED's (1.75 volt each?) plus .7 Volt for the diode is 11.2 volts. 13.7 - 11.2 is 2.5 volts. So, the current through the series string of diode,resistors,LED's is 2.5 / (4 * 7.5 ) = .083 amps. 83 ma for a LED is allot of current. So, doing this in series is problematic for high temperature enviorment.

Most likely its just one of the LED's that has gone bad. The 1N4000 series diode is rated at 1 amp, so its most likely not the problem. The resistors look to be 1 or 2 watt rated. And .083 Amps squared times 7.5 ohms is .052 watts. On the other hand a dead short at the LED cluster results in about 1.4 watts dissipation at the resistors (13/30 = .433 Amps, .433^2 * 7.5 = 1.4 w). Apparently the resistors are sized to protect against the shorting possibility.

So, while their approach of making a lifetime brake light is laudable, their execution , in saving $.50 in wire and connector contacts (by making things series)screws up the goal. As jstacks ends up paying $350 for Toyota's $.50 savings.

This appears to me to be another case of the hidden costs of living in 110 F weather. Similar to needing starter batteries replaced every other year in traditional cars...

Most people not living in such an enviorement are not going to have this problem. And even allot of people living in the "Valley of the Sun" are not having this problem.

I wonder if those LED boards are available from the parts deparment? That would have been a cheaper repair. Slip out a board, and put another one in.

 

I belive the diode is to isolate the brake light circuit from the tail light circuit.

One leg of resistors is 12.5 ohms while the other leg is 30 ohms.

They drop 12v across 30 ohms for the tail light and 12.5 ohms for the brake light.

 

Because the LED light bulbs you see at Pep Boys are not-even close to bright enough. I had trouble seeing your photos, but the LEDs used by Toyota are probably high-wattage "Cree" type LEDs which actually require heat-sinks to keep from burning out.

Probably because they consider break lights more safety-critical than the others and, in general, properly designed LED lighting is much more reliable. I would have preferred that they used all LED tail-lights, even with the extra cost.

 

I do not like LED taillights. They flicker, and that messes up your depth perception when it is moving across your field of vision, like at an intersection. Your eye won't see the flicker at center, but when they are at the corners of your vision, it is noticable. This is when you need to see them most! This is a function of eye latency. Try looking away from them quickly, and you will see a series of dashed lines, not a continuous streak. This makes it VERY hard to judge their distance.

Frankly, I am surprised they are legal for taillights.

 

LEDs are vastly superior for tailights. The illumination time for LEDs is almost instaneous versus a very noticeable lag for incandescents. That precieve amount of lag can greatly effect reaction time and stopping distance for following cars.

 

I just had both brake lights go very dim at once while the spoiler light was fine. This occurred intermittently as people would tell me my brake lights were out and I would later check them and they would be working. Finally they stayed dim.

Odd thing #1, the passenger side had a slight irregular flicker to it and one led was not lighting at all. The driver's side was just dim.

I then discovered a brake switch recall and suspected the switch. I was told by my dealer that my VIN was not affected by the recall.

Odd thing #2 was when I left the brake pedal depressed for an extended time, 40 minutes, they got brighter! They dimmed again when I released the pedal. I thought about the switch again.

I went to the dealer who spent 5 HOURS diagnosing and told me the led arrays were both bad. $800 to change them out. When my adrenaline subsided, I got the story of how the "technician" went through the entire procedure and was on the phone to Toyota to anal-ize the problem. A total check of the electrical system, a blown fuse was a created during the episode, causing doubt in my mind, and a total re-boot of the system concluded that the lamps were at fault. Both at once? For no apparent reason? A suicide pact?

Odd thing #3, during the ordeal, he did experience a momentary bright LED event that could not be repeated or sustained. Keep in mind, it's just a brake light we are talking about here. Finally, I decide to shell out the money because the possibility of future failure looked likely and at least this way, THEY would have to fix it. Again.

The car has given me 114K of trouble free use so I still feel I'm ahead in the game. I expected to have some repair at some point, this was never in my radar, especially at this price. A very unusual car indeed.
I don't hate the car, just disappointed that this tarnished a otherwise wonderful relationship.
Nick in Honolulu.

 

One LED bulb of the brake light on the driver side of my 2007 is also out. My car is only at 48K miles, ugh. I haven't decided whether to change out the tail light now (so unreasonably costly) or wait until another bulb goes bad. The brake lights are still bright enough for others to see, just a bit dimmer on the left side because of that one broken bulb.

 

Next time someone has this problem, contact me, and I can fix it for much less. It is easy to remove and replace the rear light assembly.