touch halogen, lose low beams if installing

Although I like to avoid responding to my own post, it's been over 12 hours (okay, okay, people have to sleep :) and found the answer in the shop manual. Big, bold capital letters, the manual states do not touch the bulb with the fingers because "REDUCED LIFE" will ensue. I would say < 20 minutes of [on low] bulb life is, ahem, reduced life. Yes, indeed.

I guess I forget these bulbs are halogens and this is my first time replacing a halogen headlamp bulb. I'm kind of slow in that regard. And the previous vehicles used non-halogen bulbs before. Not bad, just more than 10 years behind the curve, at a very minimum.

The instructions for the relay were, well, I'm still looking for them. The index said go to 8L-3. And then 8L-3 says to go to 8-E for the instrument panel. Uh oh, this is what I was afraid of, taking apart the dashboard. But since I cannot find exactly the headlamp switch, no problem! It's likely not the switch or whatever allows the current to get to the headlamp since only one is gone. It would not make economic sense to have a left and right relay or switch. Not much logical sense, but would do I know. I messed up replacing a simple halogen bulb.

Years ago, halogen bulbs (known then as "quartz Iodine" or just "quartz" bulbs) were made out of fused quartz. If you touch fused quartz, skin oil gets on it. When skin oil is heated to the high temperatures found on an operating bulb, it devitrifies the quartz. The result is an opaque fingerprint-shaped spot, or a blister on the bulb, or a severely balooned area of the bulb, or a shattered bulb. Which thing happens depends on the type of bulb and how hot it is.

And so we were all carefully taught never to touch the bulb. Never touch the bulb! If you do, clean it with alcohol! Never touch the bulb or it'll fail quickly! Never touch the bulb or it'll explode! Never touch the bulb!

Thing is, most automotive halogen bulbs are now made out of hardglass, not quartz. Hardglass doesn't devitrify or do anything else untoward if you touch it and then light the lamp. No opaque spots. No blisters. No shattering, no ballooning, no exploding, no shortened life. Hardglass does not know or care it's been touched by human hands. So, from a bulb-health perspective, the "don't touch!" warning is thoroughly obsolete.

It's still not a great idea to get the bulb all oily before installing it, because the oil will burn off and the oilsmoke will condense as dirt on the inside of the reflector and lens. But that's a different matter.

So, no, you didn't cause short bulb life by touching the bulb. There are several causes of short bulb life (low bulb quality, high or spiky line voltage, insecure bulb mounting, etc.). Take a close look at the failed filaments: Are the ends broken cleanly off, or are there little round globs of molten metal either at the broken ends or rattling around inside the bulb?

No.

No. The left bulb does not know or care the condition of the right bulb.

Headlamp switches and relays are usually not difficult to replace.

Very, very stupid idea. The headlamp wiring in most Mopars made in the last few decades is thoroughly pathetic (long lengths of 18ga and 20ga wire). If you tap into the left low beam wire to feed the right low beam, for instance, or do anything similar, you'll be making a bad situation even worse, aggravating the portion of your vehicle's poor headlamp performance that is caused by the marginal factory wiring and throwing a

Depending on the model and year, you may not have two hots and a ground. Chrysler uses ground-switched circuitry on some models.

DS

Nope. That warning's been in there since the very first halogen replaceable bulb appeared on a US-built Chrysler product in 1969. Back then, with quartz bulbs, it was applicable. It no longer is.

You did not cause this by touching the bulb.

DS

Thanks Daniel, very informative (as usual)

---Greg---

I did a quick peak at the bulb. I am waiting to put in another new bulb tomorrow. I'm having trouble getting the plastic hold-down screw nut to screw back in. To my surprise, both filaments seem intact. This is a Phillips 9004. I will put in a Sylvania 9004LL tomorrow. The filaments in the Sylvania, to my uneducated eye, appear somewhat more robust and not so flimsy.

The bulb may have failed not because I touched it (as you pointed out) but because it is not secure in place with the screw nut. It's not coming out and appears to be stuck but maybe my jostling it around around messed it up. Or keeping it in the little drawer under the passenger seat for 4-5 years probably did not help matters. The length of time and the bumps and vibrations of all those year probably weakened the filaments? But the highs work, so don't know. The high's filament looks about the same as the low's filament so one would think they both would be bad.

That's good to know because I could not glean this info from the factory manual with a first glance. I was hoping it was just a relay or some such which I could grab from beneath the dash - but that was on cars built long ago.

There are three wires leading to the socket so I guessed two hots, low and high, and a ground. I don't know what ground-switch circuitry is. The ground completes the circuit so acts like a switch then? Instead of switch the hots, one switches the grounds? Interesting.

Thanks for your informative reply.

Sometimes filaments break, with the two ends at the break staying so close together that you can't tell by looking at them that there is a break - this will often be the case if the filament broke due to shock rather than burning in two. If it is in fact broken, check the filament with a multimeter for continuity - if this is the case, you might even get an intermittent connection by shaking the bulb around a bit with the meter connected thru it. If the filament is solid good but not lighting in the vehicle, then the problem is elsewhere (connector, wiring, whatever).

Or broke the one. That would be consistent with a break due to shock and intermittent operation (as the broken ends move around from vibration, jostling, etc.).

Not necessarily - not unusual that one would break and not the other.

Yes.

Bill Putney (To reply by e-mail, replace the last letter of the alphabet in my address with the letter 'x')

Philips 9004s are made in Korea, not especially well. I've seen very early failures out of them before.

LL = Long Life but Less Light. Those "more robust" filaments you see produce less light, lower-quality light, and poorer beam focus. Not a wise choice if you're trying to squeeze the best possible performance out of headlamps that are fairly rotten to begin with, fed by lousy wiring.

Well, yeah, if it's allowed to rattle around while lit, vibration-induced failure becomes highly likely.

What's not coming out and appears to be stuck?

Um...huh? How do you reach this conclusion? The high beam filament does not know or care the condition of the low beam filament, and vice versa.

Depending on the model and year, you may not have two hots and a ground. Chrysler uses ground-switched circuitry on some models.

Yes.

You're right. One circuit was open, presumably the Low which does not work.

Thanks for all the good advice.

That's so. Noticeable difference between the LL and the Regular for output. Not a lot but definitely the LL is a less bright. Good advice to avoid the LL.

I believe the 9011 and 9012 bulbs use quartz and not glass.

Richard.

Nope, they're hardglass.

About the only quartz automotive halogens still on the market are some of Philips' European-market, European-type bulbs (H1, H4, H7) made at their Aachen (Western) factory. Their North American market H4s (9003/HB2) are hardglass, all their H3s are hardglass, as are all their bulbs from the Plauen (Eastern) factory.

DS