Headlights-Low Beam

Possible causes:
Vibration.
High voltage.
Inferior quality.

 

I have that blub burned out now how hard it is to replace your self ?

 

Is that like a "bulb?"
Sorry, couldn't resist.
After all it is National Punctuation Day.

 

Here's something, second gen though:

 

Here's Repair Manual info. Pretty dense. Bear in mind, they seem to insist on tearing the car half apart for pretty much everything. Sometimes warranted, a lot of times not.

 

Halogens burn out not from too high voltage but from too low voltage. There has been some discussion that the power wire to the headlamps was too thin on early 3rd gens. This would result in too low voltage, causing the bulbs to fail frequently. I think there is a TSB on this if my mind is working correctly in recalling what I read a month ago.

 

The wires on the Prius headlights are more than adequate to transmit 12v without significant energy loss. This is BS.

 

I'd never heard that, so I did a bit of research. I think an insufficient wire would be more likely to cause overheating in the socket, rather than impacting the bulb longevity directly. That's probably the cause of premature failure.

 

I believe that headlights run in series when they operate as daytime driving lights. This could lead to higher current in the wires I think.

 

Nope, that would be for highbeams. And the lift back doesn't use highbeam DRLs.

It's my opinion that bulbs burn out primarily from power instability at start up, when people leave their light switch in the on position all the time.

SCH-I535

 

Depends on your location. In Canada, the highbeams on half-brightness are day time running lights. They come on automatically at start up (or at release of parking brake?), and shut off if the light switch is turned to parking or head lights.

 

A small wire definitely could reduce the voltage; by my math, with a 12V/60W light bulb, and a 10-foot run of copper cable, anything smaller than 22 AWG would cause a 1V drop, which is a fair amount. I don't know what it takes to throw off a halogen bulb, though. Of course, 22 AWG is pretty small, although there would be other resistances (like for connectors) that would cause more voltage drop, so a safe gauge would probably be quite a bit larger than that. I'm not sure how a small wire would cause the socket to overheat as you suggest. (It would cause more power to be dissipated along the wire, but in the case above, that would be a 5 watt power dissipation over a 10-foot cable, which would be unnoticeable unless you bunched it up.)

No, the headlights in series would produce a lower current. This is Ohm's Law; V = I * R. Voltage is Current times Resistance. Light bulbs are basically just resistors (about 2.4 ohms in this case) that dissipate a lot of power, which causes them to heat up and glow. When you place resistors in series, their resistance adds; so to keep the voltage the same (since it's still the same 12V source), the current must be half as much when the resistance doubles.

 

A lot of modern cars use PWM or pulse width modulation from the ECU that controls the light circuit to reduce power/intensity of the bulbs rather than rerouting to an alternate circuit.

SCH-I535

 

just buy and put in HID conversion kit.

OEM bubs lasted ~1.5years, and went out almost at the same time (1 mo later?). IMHO it is more cost effective to replace them with HIDs as they last longer. HID H11 kits down to ~30-60$ per set, as much as the pair of incandescents .

Got them in low beam and another set in fog lights. 3 years - no failures so far.

 

the wife has a 2010 genIII that has HID lamps. And over the last year I've changed out low beams 4x's and now last night she limped home with both sides out. I've asked at dealer about a SB that I had read they said no the vin # wasn't in that group. All was good until about 1 1/2 years ago then 1 side or the other would go out which for that vintage and the amount of driving with headlights on seemed ok. But seems it's getting to be a every 1-2 months changing out bulbs. And let's rule out the fingers on the bulbs(heavy truck mechanic for 35+ years)-- tried dealer bulbs-- brands- styles within brands (silverstars.. plain Janes...ect) car has been relatively cost free for 5 years now many odd things acting up and only has 140,000 mls. on it 95% hiway miles. Bought more bulbs for this car than in 45 years of driving all the others combined/.. Something had to have changed but as of yet haven't zero'd in on it.

 

Hermit, the 2010 doesn't come with HID lowbeams. Either they were were replaced with aftermarket hids, or you have halogen bulbs.

You say you tried silverstar bulbs, so that leads me to believe you have halogens.

One question, do you, or your wife leave the headlight switch in the on position? Doing so can cause the bulbs to fail prematurely in some cases due to voltage fluctuations present at startup.

 

driver side is kind of easy... passanger side is more difficult (the windshield fluid reservoir is in the way) it also depends how "small" your hand is.

it is doable ... my advise is to practice with the old bulb to try to put it back... also when puting in the new put the bulb in firs and attach the cable afterwards.. NOT LIKE what the manual says.. it is a lot easier that way (in my opinion).

make sure not to touch the bulb by bare hand or with anything dirty...

 

There is a reason. Please see T-SB-0204-12. We have a 2011 Prius in which one dark night My wife could have been killed when both low beam lights blew out. Before this we had LB light problems and the service dept. never told us about this T-SB. I had to find this T-SB myself and it was completed this last July at my request. These problems are caused by a wiring engineering problem.