Blistered HIR1 in high beam (and DRL) service

My friend sent me this pic of a burned-out Philips HIR1 from his RX300.


Interestingly, the top of it (that is, what was the top of the envelope when installed in the lamp, obviously this is rotated) was blistering. The other bulb (which was removed to become the spare, replacing the HB3 previously slated as the spare) was fine.

(Note: Bulb mishandling was not involved (envelope never touched but for wiping it (and any other parts that go into the lamp assembly) down with isopropyl alcohol).)

Also interestingly (and annoyingly) is that one failed high beam bulb means no DRL function-- it seems the voltage is halved by running the lamps in series, not through some other means of voltage control (PWM/buck convertor/resistive load). This means my plan to have the DRL extinguish on the side the turn signal is active won't work unless I get really creative. Bummer!

I have had a puny 921 bulb blister before, makes me think a manufacturing defect in uneven thickness of the glass envelope possibly?

Alaric Darconville said:

Interestingly, the top of it (that is, what was the top of the envelope when installed in the lamp, obviously this is rotated) was blistering.

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This is pretty common in high beam bulbs operated at reduced intensity in DRL mode. High beam DRLs generally run at about 50% of rated voltage to provide about 10% of rated output. This low-voltage operation means the bulb operates for significant amounts of time without the capsule walls reaching a high enough temperature for the halogen cycle to operate (or operate efficiently). Tungsten boiled off from the filament condenses on the relatively cool envelope wall, gradually opacifying and blackening it. It happens most above the filament, because convection carries the evaporated tungsten mostly upward from the filament. Sometimes you'll see a relatively clean area directly above the filament (because it's hottest) but a dirty area surrounding that clean area. The affected area of the bulb glass then runs hot, because heat energy can no longer escape through the opaque area. Eventually this area of the glass gets hot enough to begin melting, and the bulb's internal pressure blows a bubble/blister.

Why in some bulbs and not in others? If the chemistry inside the bulb is imperfect -- not enough getter, too much getter, maybe a little bit of oxygen that shouldn't be there, etc -- it increases the likelihood of deposits accumulating on the glass.

Replace the bulb and move on with life.

-Virgil- said:

Replace the bulb and move on with life.

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He did! (Both, presumably!)

For me, the biggest thing was that my plan to modify the DRL functionality (extinguish the DRL on the flashing turn signal side) now seems to be much more difficult than originally planned.

I will suggest either a more-frequent change schedule, or more-frequent (and longer duration) high beam usage. The latter may help keep the envelope cleaned up.

And now he reports a burned-out low beam.

Also, the fog lamp also burned out a month or so ago and those are super-rarely used-- sometimes as a "pull into the driveway to scan for cats under the other car" light.
ALL THREE bulbs were on the right side. Weird!

As far as the high beam goes, I think I may disable the DRLs and look for good LED DRLs to install instead. This will keep the high beam bulbs more clear and reduce heating inside the lamp assembly.

Alaric Darconville said:

ALL THREE bulbs were on the right side. Weird!

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If that happened to me, I might take a look and see if all 3 bulbs shared a common ground. Okay, so it's a Toyota, which probably means it's a switched ground headlight system, but I still suspect something along those lines. Folks always look at positive-side voltage, but it takes a ground to complete a circuit. A flaky ground can lead to burned out bulbs, too.

eggsalad said:

A flaky ground can lead to burned out bulbs, too.

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A flaky ground would be evident to the operator as the lights would visibly flicker, or the lamps would occasionally fail to light, or would be a lower intensity. I'm more apt to suspect vibration.

Alaric Darconville said:

A flaky ground would be evident to the operator as the lights would visibly flicker, or the lamps would occasionally fail to light, or would be a lower intensity.

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"Flaky" being an imprecise term. You're right, if that ground is bouncing between zero and infinity ohms, the driver would see flicker. But if it's bouncing between zero and a few hundred ohms, the flicker would be less obvious, especially on well-lit roads, but still cause the voltage to the bulb to bounce around.

Alaric Darconville said:

I'm more apt to suspect vibration.

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That theory is as good as any. Perhaps there's an out-of-balance tire or worn suspension/steering component on that side.

eggsalad said:

You're right, if that ground is bouncing between zero and infinity ohms, the driver would see flicker. But if it's bouncing between zero and a few hundred ohms, the flicker would be less obvious, especially on well-lit roads, but still cause the voltage to the bulb to bounce around.

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For so short a period of time, and with such a small variance in voltage that the filament doesn't flex that much. And if that fog lamp bulb had 12 hours on it, I'd be surprised.
I'll still give the thing a going over just to be sure, but the times I've driven it at night and in the unlit areas I never noticed anything.

That theory is as good as any. Perhaps there's an out-of-balance tire or worn suspension/steering component on that side.

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Or the entire lamp assembly is wiggling around. The fog lamps are built into the same lamp assembly as the position, turn, and high & low beams.