Replace Headlights in pairs

On your show last weekend you discussed changing headlights in pairs. Every time I replaced one, the other would burn out in a day or two. I cannot remember where it was written (on the headlight package no doubt) but the advice was; one, dont touch the bulb glass and two, replace in pairs. It did seem to be common knowledge, but heck, i am just a girl.

I only replace the headlight bulb that burned out. Replacing in pairs is just marketing. It sells more headlight bulbs. There is no science behind it. I’ve never had two headlight bulbs burn out within days of each other. Your experience may be different, but it’s never happened to me in more than 40 years of driving.

The part about not touching the bulb glass is absolutely true, however.

There would be nothing wrong with changing both (or all four) headlight bulbs as a preventive measure. I just can’t see replacing bulbs that still work.

Agreed ; not needed. But if you carry a supplies/tool box ( my daughter does ) include a few spare bulbs of importance with your basic pliers and screwdriver stash. Headlight, tail/brake light, and a few fuses are nice to have.

Well, about 20 years & 200,000 miles ago I replaced the drivers side sealed beam on my 87 Ranger. The passenger side still works just fine.

About 2 years & 40,000 miles ago I replaced the drivers side low beam bulb on my wifes 02 Sonata.
The other 3 headlight bulbs are still working just fine.

And about 1 year & 20,000 miles ago i replaced the drivers side brake light bulb on the Sonata & all the other rear bulbs are still working just fine.

If it aint broke dont fix it.

I’d only replace the lamp that’s bad. The only exception to this might be if the lamp is tough to get out. For example, some late 80’s Ranger pick-up trucks require that the grille be removed to change the headlights (really poor engineering). In this case, I might be tempted to change both.

Exactly right & I had a few choice words for the genius at Ford who designed it that way.

Remove the grill to replace the headlight. Go figure.

I bet the same engineer decided not to put an access panel in cars so that the fuel pump and sender could be replaced without dropping the tank.

My daughter’s Honda Civic bulbs are a nightmare to change too. I wonder, why, oh why, do they do this?

I by necessity do a lot of highway driving, much of it in the dark. Too much of it in bad winter storms…in the dark. When one bulb goes I change them both. To me it’s a safety issue.

On my car it’s also easy. Both are turret style, twist and pull the holder, unplug the bulb, and reverse the process. And there are no components in the way. No battert there, no power steering fluid reservoire (like my daughter’s Civic), no nothing. Super easy.

The “don’t touch the bulb” thing is what’s commonly recommended. So I do it. I’m not sure I believe it, but it doesn’t cost anything to do it. The theory actually comes from quartz halogen lamps. The quartz bulb is very close to the filament, which gets very hot, hotter than the glass in the old style bulbs. The theory is that deposits from your skin will heat up and create “hot spots” in the fused quartz bulb and possible failure. I don’t know if that’s true, but why tempt fate?

I bet he owns the patent on the special offset box wrench you need to remove the alternator, too.

Your procedure and preference comes from your personal experience,has nothing to do with being a girl,you degrade yourself to play that card.

“…but heck,i am just a girl”.

The Chevrolet dealer where I purchased my 2006 Chevrolet Uplander assigned me to a service advisor who was a very attractive young lady who was very knowledgeable about cars, and very pleasant to work with.

I have had several papers that I have presented at national conferences and published concerning the performance of women in mathematics over a 14 year period at both a major state university and a good private college. In both general studies mathematics and beginning calculus, a higher percentage of the female students enrolled in these classes did satisfactory work than did their male cohorts. In fact, a higher percentage of the female students in these classes earned an “A” in the course than did the male students. Don’t put yourself down.

Most people tend to define ‘end of life’ for automotive headlamps as when they completely fail to illuminate. In fact, their output intensity is degrading constantly as they are used. The aging profile is non-linear such that the output loss occurs fastest in the early stages of their life, knees and then the slope becomes less severe but still constantly degrading. The loss of intensity is caused by a number of factors but the most predominent being; electrode/filament erosion.

The erosion of the filament increases its resistance over time and consequently its output intensity decreases. For arc lamps, the electrodes wear and increase the gap. Redeposition of the electrode material onto the lamp envelope also reduces output by absorbing some of the emitted energy.

So, while the lamp may not have failed totally, it has lost a relative amount of output intensity over the time it has been used. It’s kind of like a dirty windshield. It happens over a long enough time that when you finally notice it, it’s gotten pretty bad. If the lamps have been in service for a long time, when you change the one, it might be obvious that the older one is less intense than the new one. Complete failure to illuminate may not be the defintion of end of life for everyone. I have a hard time seeing at night. I may be more sensitive to headlamp output than someone with great night vision.

Another consideration has been brought up as well- tolerance for repeating the labor. When I was younger, I would eek the most possible life out of everything. I had way more time than money. As I got older, my time became more valuable and my tolerance for repeating work diminished. Now, if one fails and it’s not an infant mortality thing, I change both to avoid doing the job again. Especially true if the job is difficult or unpleasant. YMMV.

“but heck, i am just a girl”

TwinTurbo addressed the headlight issue beautifully, so let me just respond to the above comment.

I worked my way to my BS in mechanical engineering by teaching auto mechanics in a junior college. My 101 class included people who aspired to be professional mechanics as well as people who just wanted to learn the basics so that they could be smart consumers of mechanical services. Roughly a quarter of that class was female.

I found that the females were consistently among the best of my students in both lecture and lab.

The junior college night school teachers had a saying - “The problem with teaching adults is not what they don’t know - it is what they do know that ain’t so.”

Remove the grill to replace the headlight. Go figure.

I have the same feeling about why they decided to let the design staff out of their cages and eliminate the basic sealed beam headlights, that cost $4.00 and take less than five minutes to replaces using just one screwdriver.

I totally agree. Bring back the glass sealed beam headlights. They’re cheap, don’t turn fuzzy and yellow, easy to change (unless you own an 80’s Ranger), and are all removed the same way.

Of course you need to have headlights aimed every time they you replaced a sealed beam unit. In my cars that use halogen bulbs. The bulbs can be replaced without tools, in under 5 minutes. The ones on the Mustang are particularly easy. You just open the hood pull two retaining pins out, the whole headlamp assembly slides right out you remove the dead bulb, put the new one is slide it back into the car, put the pins back and you’re done.

Not true! You only had to re-aim the headlights if you messed up and turned the adjusting screws instead if the lamp mounting screws.

About ten years ago I bought a seven year old car of German manufacture. One of the new fangled headlight bulbs died within a week. Since they were even more expensive then than they are now, I bought and replaced one. A week later the other one died. I drove it for four years and never replaced another one. I have often wondered if I used the turn signal switch to actuate lights for passing, which illuminates both the high and low beam filiments, where the original owner didn’t. I guess he was a slow driver. He did wear a hat…

I still only replace one bulb if it’s burned out.

It sounds logical to replace in pairs. “if one is worn our, the other is soon to happen.” Or, so I thought.
When I was told that the price of one halogen bulb was something like $120, I did not replace the second one. That was 2-1/2 years and 30,000 miles ago. Both the old and the new are still burning brightly.