My Toyota Prius 2010 caught fire

We couldn't have guessed the construction details, but those critical numbers are about as expected, and about the same as I predicted in previous posts here. I did hastily assume 60W/12V=5A., which isn't so accurate. The packaging on the Sylvania bulb I just bought implies they consider normal operating voltage to be 12.8v. Thus, 55W/12.8v= about 4.3 A; 4.3A×0.12ohm=0.52V.

Yes, excellent investigation and report, ChapmanF !

Now, about those people who are still recommending installing relays to minimize the voltage drop ...

 

Ok, so I haven't remotely gotten around to applying the TSB fix, but just to see what the pre-fix condition is, I took voltage readings at the low beams in READY with the bulbs in place and operating. The fierce glow in the background is the bulb hanging loose out of the reflector, with backprobes stuck in the connector:



For a Sylvania basic, anyway, the expected operating voltage is 12.8:



At rated voltage, the Sylvania basic is expected to last 270 hours:



Seems like the original 2010 wiring is so not-skinny-enough it is delivering more than a whole volt extra to the bulb. If the thirteenth-power relationship holds, going from 12.8 to 13.8 ought to knock the expected life from 270 down to about 102, or just about one year for Sylvania's "average" driver. A bulb a year could be annoying. (Heck, even a bulb every 2.7 years could be annoying ... I don't think I ever changed a headlight bulb in eight years driving my Gen 1...)

Under those conditions the bulb is probably dissipating closer to 64 watts than 55; the 0.12 Ω TSB fix should end up knocking off about 0.54 volts, bringing the bulb power down to about 59 watts and expected life back up to 167 hours ... 20 months for that "average" driver. I assume they didn't want to trim the voltage more than that and give up more light.

I don't think I'm going to jump hastily into installing this fix. If I read things right, the original wiring to the headlight may be aluminum. The 82114-47010 TSB part is copper. Toyota's wiring manual "harness repair" section has really, really specific rules for splicing on aluminum, including a different crimp barrel, different crimp tool, and adhesive-filled weatherproof heat shrink tubing, compared to what they specify for splicing copper. (And yes, the aluminum-specific procedures are the ones being given in the TSB.)

I think I'll wait on this until I have the stuff to do it strictly by the book ... bad aluminum-to-copper splicing was a notorious factor in house fires in ~ 1970s USA....

-Chap

 

I think you may have hit the nail,on the head,
I've coped with aluminum-copper junctions in house wiring and seen such wall outlets catch on fire, etc. Given lack of strong, specific training in doing those aluminum-copper junctions to the Toyota techs, making mistakes that could easily lead to fires seems likely to me.

 

As far as I can tell, Toyota does make a real effort to train the techs. In the training course book for their T623 Electrical Circuit Diagnosis (available under the "Technical Training" tab on techinfo), page 138 is all about aluminum wire, with a boldfaced caution about using the special crimp sleeve, tools, and procedures.

I just now found that book, and learned Toyota uses the insulation color lavender to indicate aluminum wiring. Sure enough, the factory headlight wire is lavender (and the TSB repair piece is white/black, I wondered why they didn't match the color, now I know...).

-Chap

 

Is that the ground or "hot" wire? The other one is copper? Thanks!

 

The ground wire is white with a black stripe, no lavender, so going by what I read about their color code, it would be copper.

The +12 wire is lavender, or, hmm, the 2010 wiring diagram just calls it violet:


That technical training book suggests aluminum wire would be called out specifically as lavender:


I don't know just what to make of that, unless maybe they modified the color spec since 2010 (the PDF file for this training book carries a January 2016 mod date).

Anyway, the splicing instructions given in the TSB are definitely the aluminum splicing instructions, and the crimp sleeve part number and crimp tool they show are the ones for aluminum.

-Chap

 

So why wouldn't it be easier and possibly safer to splice the add-on copper resistor wire into the ground wire instead? There may well some logical reason why that would be unsafe or impractical, but I'm not thinking of it.

They could've made the add-on harness with a connector that would mate with the plug on the OE harness, thereby avoiding the need to make such a critical and potentially hazardous splice in an awkward location.

 

Bump. I lost both low beams on a long trip. I'll try to make an appointment for the extended warranty (program ZHB).

Hope I'll nor get the car on fire instead.

 

me too.

 

They should solder the wires, then seal them. I forget the type of solder you use to join the two different metals together.

 

Crimp connections are very good when properly done; my preference would probably be to install just as directed, using the proper barrel material, proper crimper, and proper sealant. And possibly doing it myself rather than leaving it to whoever shows up in the dealer shop that day....

-Chap

 

If you want something done right, do it yourself.

 

Depends on what you're doing. Somethings I know there are pros who will doing a much better job than me, and/or I really don't want to do it. Surgery, steep slope (and/or high) roof repairs and garage door torsion spring tensioning are a few that spring to mind.

I'm about ready to add house painting to that list too: last time I let the pros do it, and it was fast and well done. Still, they don't have the time or patience to prep properly, scraping off loose paint, so maybe a compromise: I scrape, they paint.

And DIY is not infallible; everyone can have brain farts. Over the years I've:

1. Started pouring motor oil into an automatic transmission.
2. Left the oil filler cap off.
3. Snugged wheel lug bolts but neglected to torque properly.
4. Swapped the intake and exhaust valve clearance spec's.
5. Swapped the connectors for washer fluid motor and turn signal (the result was hilarious...)

That's about it I think. I managed to recover semi-gracefully from all of the above, but yeah: stuff does happen.

 

Man, that Prius fire is scary. On the local news recently, they showed two Tesla fires.

I've done the oil filler cap being left off.
And accidentally applied 2 rubber gaskets when screwing the oil filter back on. (Camry) While driving down the road, I looked in the rear-view mirror and saw a looooooonnnnggg trail of oil behind me.
And just recently, TWO TIMES, I started to walk out of the house with no pants on! Just my underwear. I actually made it outside one of those times...

 

i saw a gasser burn up once, spectacular!

 

Maybe it's that cold weather messing with your brain!

I've never put motor oil in an auto trans.
Did leave the oil filler cap off, but put it back on after starting the car and realized it was off.
Only once forgot to tighten the lug nuts because I was interrupted several times, but only back the car about 6 feet.
Never used the wrong clearances for valves, because I carefully checked before checking.
Have NO idea how you could have got the connectors wrong for the washer motor and turn signal.
Pretty much physically impossible.

All of those are carelessness. And of course everyone makes mistakes.
And there are some people who should NOT be doing anything!
I've worked with some of them. I wouldn't trust them to remove a valve cap on a tire!
And if you just CANNOT or do not want to do a certain job, then fine. 95% of the things I can and will do myself.
And will continue until I am physically unable to, then I will watch the person doing what I can' to make sure they
do it correctly.

If you take your time, pay attention, double and triple check, you CAN do the job correctly the first time.
Plus there are plenty of youtube videos out their!
Everyone needs to learn their limits. I usually don't mess with 120 vac. Because ac doesn't let go! I've replaced
switch, sockets, circuit breakers, but I wouldn't try rewiring my house. I just don't understand it enough. Besides
the fact it's against the law. But since that's something that has never come up....it doesn't matter.

If you don't feel you can do some, or just don't want to, fine. Be thankful you have the money to pay someone
to do it for you. And they have more money to support their family!

 

I passed an Escalade on fire a couple of weeks back.

The flames were rolling out of the dash.

Just another day on the California highways .

 

huh. and here i was beginning to believe that only ev's catch fire.

 

As I approached the highway maintenance crew was running away as it was above their skill set.

Black smoke was rolling out so I made sure I had the vents on recirc .

It was gone the next day I drove by.

 

hope the folks inside weren't.