Just noticed class action filed for bulb burnout problem

Pin 16 of the DLC3 connector is just an unswitched, always on, +12V bat connection; dongles can use it for power. The ScanGauge has an A/D chip and just measures its voltage; unlike other data, it's not being read from some ECU somewhere. (If you press one of the ScanGauge buttons to wake it up, it can happily show you the voltage there while the car's off and the ECUs are asleep.)

That circuit just branches off on the wiring diagram from some other circuitry under the dash, one or two fuses and a fuse link away from the battery itself and from the DC/DC converter. The wiring and fuses are all resistive and have non-negligible voltage drops when typical currents are flowing with the car on, hence the voltage seen by the ScanGauge (and also on the MFD diagnostic screen, for the same reason) is noticeably lower than what you measure right at the battery.

What you see by waking up the ScanGauge when the car is otherwise off will be closer to battery voltage (less current flowing to result in voltage drop). But when the car is on and currents are flowing, there's a difference.

-Chap

 

I'm not familiar with scangauge and use elm327 clone. I just checked and it has A/D converter.
I'll compare the voltage readings and report back.

 

TAK1313, I will be curious to see what happens with your bulb testing. I purchased my 2010 used with 60K miles and am now at 203K. My commute has me using the headlights for 3.0hrs a day during winter, and slightly less in the summer. My bulbs usually fail somewhere around 6-8 months, neither side fails more than the other. I make sure to turn on the headlamps after the inverter starts up to minimize the voltage spike to the bulbs. I tried some of the Sylvania silverstar high performance bulbs, they had more light output, but an even shorter life.
I think as you and others say it is due to the higher voltage supplied to the bulbs in the Prius since it uses an inverter to charge the 12v battery rather than an alternator like a typical vehicle. Reducing the voltage to the bulbs will obviously make them last longer, but with the tradeoff of less output.
I tried the OPT7 LED bulbs, but my experience was that they had slightly less "vision" or distance than the filament style of bulbs. I had tried some HID's with another vehicle but was disappointed with the lifespan of the ballast.
I understand the class action suit for the older Prius GEN 2 HID bulb failures since the cost of those bulbs was much higher, but I don't really see the point in the case of the GEN 3. But if enough people complain I guess something might happen. For me I'm very happy with the reliability of the vehicle, I just keep a pack of bulbs in the glove box and replace as needed. As we speak the RH bulb just failed 2 days ago, just waiting for my Amazon order to get here.

 

Before you replace another lamp did you look at Toyota's T-SB-0204-12? It discusses the issue and offers a replacement wiring harness as a repair - see upload (I got it from the NHTSA gov site)

 

I bought both of those harnesses (same part number, you just need one for each side) and the parts to go with, right after I bought my 2010 (the seller reported having had to change the lights often). Oddly, I haven't gotten around to putting them in yet, and I still haven't lost a light (it'll be a year next month).

If they last that long for me, I'll probably never bother pulling the bumper and fussing with the whole harness installation. Some of the original car harness is aluminum, making a safe crimp connection between copper and aluminum requires not just the exact specified crimp barrels (which I have), but the specified tool, which I haven't bought yet, and is a bit pricey.

Maybe the seller was using high-output/short-life bulbs and being annoyed at the short life, but put in standard ones just before selling to me, and so far those have lasted long enough to not annoy me.

I have spares in the glove box, of course.

-Chap

 

I too have never had a bulb burn out on me (actually in any car that my wife or I have ever owned). We usually buy cars during the last year or two of a generation and buy it with 1 or 2 low-mileage years. Then we hold onto it for about 5-6 years. This time we'll probably hold on the these Prius' for 10 years. As far as the headlight issue, it could be that some of the original harnesses have an intermittant failure that only reveals itself in certain conditions. Perhaps the original wire/crimp combination was faulty or the cimp was not performed correctly, and now under certain conditions the lights fail. Or perhaps the existing wire is of insufficient gauge but just barely so only causes an issue in CTE mis-match environments? Who knows...

 

We know a fair amount; it just happens to be in a thread you wouldn't expect, just because that's where most of the discussion happened. here's a post describing the repair wire harness in detail, and here's one with voltage measurement at the bulb in operation (the measurement that counts), pre-repair. (The discussion does extend above and below those two posts.)

-Chap

 

Reading that TSB was interesting. I don't think I ever used a hammer on a light plug before.... (See figure 3)

I remember a couple of years ago I got a Check in the mail as part of a class action suit against Sylvania. It was for false advertising but hey, It was enough to cover a good cup of coffee.

Sylvania To Pay $30M To Settle Headlight False Ad Suit - Law360

 

It does look like a hammer!

It's not. That's the plastic handle of Terminal Removing Tool "F", which is nothing but a large plastic handle on a small metal poky bit, to release the terminal from the housing.

-Chap

 

This part makes sense will check it out

I am not sure about this, I wouldn't expect almost 1 V drop on the wires even on a 20A circuit that would be 20Ax20Ax1V/20A=20W loss on the wires?? that would heat up in a wire-channel quite easily.

 

Your math is right. If you were to poke around with a thermal imager, I suspect you'd see the fuses and fuse links showing up brighter than the wiring in general, but all of it would stand out from the background.

The difference I'm used to seeing is not as large as a volt (to the usual dash measurement points, i.e. the OBD port and the MFD internal display) ... more on the order of half a volt, compared to a measurement at the battery terminals. I'm sorry I don't have more precise data; I've casually noticed the difference a couple of times when I happened to have a meter at the battery to compare to, but I haven't done repeated trials with date/time/temperature/etc.

Now, I have measured the drop in my Gen 3 from DC converter output to operating headlights at pretty much one solid volt. (And that, judging from the headlight longevity TSB, still isn't enough drop.)

-Chap

 

Man this happens to me so much - I had no idea that this was a defect in the headlights. I buy new ones every 4-6 months. So annoying. I hope they win this lawsuit.

 

Went to aftermarket HIDs over a year ago and no worries about bulb failures now.