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'09 Prius HID failure mode

I'm back after an unplanned absence (newsreader misconfig performed by me...) For the past several months one of my headlights would go out.. One time on the way to work, I noticed the driver side headlight was out, I pull to the side of the road and flip on the high beams, both lights go out! When I would get a car serviced, I would mention it and they always said they couldn't find anything wrong with the lights.

Last Tuesday morning, a mile from home, both went out at the same time. Previously, either one or the other would go out with most of the failures being the driver side. But, as I said, both went out, so I turn around and drive home, take a nap and wait for daylight. I end up driving to work and dropping it by the dealership on the way in and get a drive to work.

Last Tuesday, after I dropped the car off, they looked at the lights and the right one failed, so I had them make the repairs they said it needed. Everything seemed to work okay.

On my way back from a wedding this past weekend, a trooper pulls me over and gives me a warning for a headlight that is out (driver side). If I flip the lights off and back on, both come on. The next morning I drive into work and call the dealership and talk to the service manager and tell him what happened. He says that is the failure mode of HID headlights.

Is he giving me a line of crap?

Reply to
Wayne Dernoncourt
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Yes, I would. HID bulbs don't have a filament to break, hence the discharge part of the name. HID headlight bulbs are a variant of metal halide lamps as they have some xenon added to the halogen gas/metal halide salt mix in the bulb so that they put out usable light while cold. They are also designed to handle a hot restrike (off and back on without cooling first). When they fail their running voltage goes too high and the ballast shuts them down. They are constant current driven bulbs so too high a running voltage means too high a running wattage and too many watts melts stuff.

The failure mode you are experiencing is fairly common on the Prius and is similar to a metal halide or high pressure sodium street light that warms up to full brightness, goes out, cools, and comes on again. (repeated ad nauseum all night long)

Reply to
Daniel who wants to know

The most likely cause of the condition you are describing is failure of the HID bulbs. It is not uncommon for both left and right side to fail within a short time frame because they were made at the same plant with the same materials and get the same amount of use.

The next most likely cause of the condition is the combination headlight/turn signal switch.

I'd start with new HID bulbs first and keep the old ones.

Reply to
Ray O

On Thu, 30 Sep 2010 21:00:13 -0400, Daniel who wants to know wrote (in article ):

I'm surprised that Toyota doesn't have gizmo's and thingamabobs to restrict the voltage/current. Or is that gizmo called the "Ballast". It sounds like a safety issue - what is the expected lifetime of a bulb? I've been running the lights whenever I drive (day or night) but given the cost of the light and replacement, that may have to change.

Reply to
Wayne Dernoncourt

I have not seen any figures on the expected lifetime of an HID bulb, but it does have a finite life. If you want to extend the life of the bulb, use the DRL's instead of having them full on.

Reply to
Ray O

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