Changing headlight or foglight bulbs can be a perplexing task—especially on modern vehicles.

That’s because, on some cars and trucks, it’s a 60 second affair that simply involves unclipping the connector plug and giving the bulb a half-twist to release it from the housing socket, easy-peasy.

Yet on some others (cough*Subaru*cough) it’s a far more tedious job that can involve removing the wheel and pulling back the inner fender liner to get access to the back of the headlight assembly—then winding your hand blindly through a maze of wires and brackets to reach the housing.

…Hence why there’s no single, universal guide on how to change a headlight bulb that applies to every car, truck, or SUV ever made.

But! We can offer some general insight to help the job go smoothly and ensure your new bulb lives a long, happy life in its new home. Check out our list of five tips below, and if you have any more to add, please drop them in the comments section at the bottom of the article.

hand holding a set of automotive lights
The driver’s side foglight recently burned out on our daily driver, so we’re swapping in a set of H11 Hella Optilux Extreme XY Light Bulbs to illustrate the points made in this article. (Image/OnAllCylinders)

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5 Universal Headlight/Foglight Bulb Replacement Tips

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1. Not All Bulbs Install the Same Way! Read Your Instructions

bulb installed behind an automotive foglight
The H11 bulb in our example simply rotates a quarter-turn to release from the foglight housing, and to pop-off the H11 electrical connector you just pry back a pair of prongs on either side—super simple, but other bulb types aren’t so easy. (Image/OnAllCylinders)

Perhaps the most vexing part of headlights and foglights is that they don’t all plug into the housing in the same way.

For example, the H13 (9008) bulb used in a lot of domestic trucks is removed and re-installed with a simple half-twist of the bulb itself, to secure and lock the bulb in place. Conversely, an H7 bulb used in some late-model imports is often retained by a delicate swing-out wire clip that you have to un-latch and re-latch separately to keep the bulb secured.

In other words, make sure you know how to remove and replace the specific bulb you’ve got first—a quick internet search on your particular bulb type will clear up any confusion. This step will save you a ton of frustration once you’re elbow-deep in the job. And it’ll help you avoid damaging the bulb or, worse yet, the wiring connector or light housing.

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2. Inspect the Bulb & Keep it Clean

a comparison of new and old headlight bulb
Circled in red here, you can see the broken filament failure of the old bulb in the foreground, and the intact new one behind it. Never assume the bulbs are OK before putting them in, always do a quick visual inspection—a side-by-side new/old comparison like this helps. (Image/OnAllCylinders)

Headlight and foglight bulbs tend to get really, really hot when they’re turned on. That’s normal and not a big deal—unless you’ve got a greasy fingerprint or some other goo on the delicate bulb lens.

Oil from your skin or other contaminants often have different heat cycle qualities than the lens material, and it can create a potential hotspot—both which may negatively impact the bulb’s service life. So if you see any odd residue on the bulb prior to installation, it’s good practice to wipe it down with a clean, lint-free cloth. Then when it’s time to install the bulb, make sure to avoid direct contact with the bulb lens. (We often don a pair of disposable gloves, just to be extra careful.)

It’s also a no-brainer to give the bulb a once over to make sure everything looks normal (IE no broken filaments or loose/rattling parts inside) before you pop it into the light housing.

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3. Keep the Vehicle & Headlights Off

a foglight bulb with connector removed
You can see the exposed pins of the new bulb installed. Excessive force can bend the pins or some errant moisture can short the connector and potentially blow a fuse—or worse. (Image/OnAllCylinders)

We’ve known seasoned gearheads that leave the lights on while doing a bulb replacement—so they can see the light blink on when it’s plugged in and easily confirm that the new bulb works. While that may…may…have been OK a few decades ago, modern vehicles are far more complex nowadays.

From the engine computer to a fancy infotainment system, modern cars and trucks are packed with sensitive electrical components, which can be susceptible to damage from electrical shorts or dramatic voltage fluctuations. For that reason, you should always make sure—at the very least—to remove the key entirely and confirm that all lights in the vehicle are off.

Should You Disconnect the Battery?
There’s plenty of conversation around this question, and you’ll hear intelligent arguments on both sides. We typically err on the side of caution and disconnect the battery any time we work with vehicle electrical systems—fuel pump, HVAC, lights, etc. It’s an extra redundant step to mitigate the risk of accidental damage to your vehicle’s delicate electrical system.

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4. Put a Tiny Dab of Dielectric Grease on the Mating Surface/Gaskets

man holding a single automotive foglight bulb
Note the trace amounts of dielectric grease on the red gasket/grommet at the bulb base, along with some more grease coating the inside of the connector receptacle. (Image/OnAllCylinders)

For starters, let’s emphasize “tiny dab” here. We’re talking a small, trace amount of grease to simply serve as a thin film on the gasketing and mating surfaces of both the headlight or foglight housing and the electrical connector on the bulb. Too much will get messy (recall point two above) and, given the nature of dielectric grease, when used on the connector it could impede the flow of electricity into the bulb altogether.

We typically put a small, tiny dab on our finger and smear it down to a thin(!) film on the gasket surface—again, remembering to clean our hands thoroughly before we handle the rest of the bulb install. This will help seal the bulb housing to mitigate moisture ingress (fogging), while preventing the two surfaces from adhering to each other over the years and miles between bulb changes.

Why is this important? We’ve encountered headlight bulbs that, thanks to hundreds of engine heat cycles, have gotten stuck to the socket on the housing, which makes for frustratingly difficult bulb changes—same deal with the seal on the wiring connector to the bulb itself. Take this step and “future you” will appreciate it during the next bulb swap.

You may like this article too: What is Dielectric Grease & Why (& Where) Should You Use It?

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5. Turn it On & Inspect the Light Aim/Pattern Before Putting Everything Back

close up of front of a car with foglights on
Success! Though this particular job was very easy, other cars in the OnAllCylinders motor pool require far more complex bulb changes, which means you better make sure the bulb works before you start putting things back together. (Image/OnAllCylinders)

Once you have the bulb secured into the headlight or foglight housing, and the bulb’s electrical socket plugged neatly into the wiring harness connector, it’s now perfectly safe to reconnect the battery and turn the lights on.

Not only will this tell you that the bulb works and is installed correctly, it’ll also make it easier to spot any errant fingerprints or muck that may have landed on the headlight lens or the bulb itself. If you notice anything awry, you should wipe the area clean and re-install.

Then, check to see if the headlight pattern is consistent with the bulb on the other side!

close up of a geared adjustment wheel on a headlight housing
Need to make small, precise tweaks to your headlight or foglight aim? Many vehicles have small, geared adjustment wheels that’ll help you do it. (Image/OnAllCylinders)

Often times, a headlight housing will have a thumbwheel or other small adjustment screw or knob to help you dial-in the beam aim and make sure it matches the other side—in fact, sometimes you’ll see two, one for the horizontal adjustments, the other for vertical adjustments.

That way, you don’t blind or distract oncoming drivers. It’s not uncommon to make a minor tweak after a headlight replacement, but if the light aim is really off, it’s worth taking things apart again to investigate the issue.

Also, take the time to jiggle some wires and make totally sure the bulb is seated properly in the housing—to check that it’s not angled or sitting goofy inside. Finally, confirm that nothing is loose or rattling around.

These are important final checks, particularly if you’ve had a complex headlight job that required a wheel removal or some other not-so-fun step. After all, it’s a total facepalm move to discover something’s wrong with the bulb install after you’ve buttoned everything back up.

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Links to More Helpful Headlight Upgrade Tips & Tech

Since automotive lighting is a complex, nuanced topic. We’ve got a handful of additional tech resources that can help you out. Click the links before for more info, and if you’ve got any headlight-swapping wisdom to share, let us hear about it in the comments!

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Author: Paul Sakalas

Paul is the editor of OnAllCylinders. When he's not writing, you'll probably find him fixing oil leaks in a Jeep CJ-5 or roof leaks in an old Corvette ragtop. Thanks to a penchant for vintage Honda motorcycles, he spends the rest of his time fiddling with carburetors and cleaning chain lube off his left pant leg.