Car headlamps question
January 30, 2014 11:47 PM   Subscribe

I've just replaced the headlamps on my little hatchback and drivers were flashing me non-stop all the way home, as if my main beam was on.

When I look at the beam pattern, it IS quite high. The light thrown by the beam was about 5' high off the road.

The other unusual thing about my journey is that my boot was full of really heavy musical equipment, which it isn't normally.

It looks like I need to have my headlamps recalibrated but it's confusing as to why this has coincided with changing the headlamps (which was easy) unless it's all to do with the weight in the boot?

If you can shed any light I'd be very grateful... ;-)

I've had a look online and my car seems to take the exact same bulb for both main and dipped beams so it seems unlikely I could have mixed them up to adverse affect.
posted by dance to Travel & Transportation (12 answers total)
This may be an utterly idiotic thing to suggest, but are the lamps mounted upside down? I don't actually know whether this is even possible, but I can see how it could result in this weirdness.
posted by Emperor SnooKloze at 11:51 PM on January 30, 2014 [3 favorites]

Does your car have the little adjust switch that allows you to move the angle of the headlights up and down? It might have gotten pushed too far one way, while the bulbs were being installed, and not been adjusted back again.
posted by Solomon at 11:53 PM on January 30, 2014

How are the cars springs and shocks? Any possibility that they failed to equalize the heavy load of gear in the rear?
posted by Cranberry at 12:24 AM on January 31, 2014

It's doubtful that the stuff in your trunk makes much (if any!) difference; I'd say the problem is entirely misadjusted headlights. What kind of car are you talking about?
posted by easily confused at 3:03 AM on January 31, 2014

Many cars have an adjustment wheel with which to control how high the headlights shine. If you've got a lot of weight in the trunk, the back of the car will be lower and the front higher. Therefore, the lights will shine higher and possibly blind oncoming traffic. You should adjust the lights accordingly.

Try parking in front of a wall on which you can see your lights and fiddling with the adjustment wheel.
posted by amf at 3:38 AM on January 31, 2014

You probably need to adjust them. Any halfway competent mechanic or dealership should be able to do this for you, and it's a relatively easy procedure to DIY if you have the inclination.

There IS an adjuster somewhere - it might be a dial or a screw. The procedure is MORE OR LESS like this. I am not your mech, check your car's make/model and local laws, etc…

This is how you do it for most motorcycles - I suspect it's similar for cars. Basically - you park the car/bike facing a garage door or wall 20 feet or so away. Measure from the ground vertically to the center of the headlamp. Then mark that height on the wall. Turn on the headlight and adjust the MAIN beam so that the cutoff at the top of the light pattern is aligned with the mark.

The dipped beam is usually adjusted around 12"-14" below that.

You'll need to find what the recommended heights/offsets are for main vs. dipped beam, but you and google and a manual should be able to figure that all out. It's pretty straightforward.
posted by Thistledown at 4:37 AM on January 31, 2014 [2 favorites]

Is your car the style where you change the reflector along with the bulb or just the bulb? Because if you have seal beams then yes, they need to be adjusted after replacement.

dance: "It looks like I need to have my headlamps recalibrated but it's confusing as to why this has coincided with changing the headlamps (which was easy) unless it's all to do with the weight in the boot?"

It's possible your old bulbs (if you have replaceable bulb sytle lights) were so dim that even though the housing was misaligned they weren't bothering anyone. Now that you have fresh bulbs they are bright enough to be blinding people.

Did you use a standard OEM replacement bulb? Most of the HID conversion bulbs are completely crap with misaligned filaments that cause the light to spray all over the place instead of having a good cut off.
posted by Mitheral at 5:19 AM on January 31, 2014

The mechanic who changed my left headlight bulb a few weeks ago didn't get it properly clipped in. I was lighting up rooftops. Easy fix at another shop.
posted by SLC Mom at 6:34 AM on January 31, 2014

you almost certainly got them out of alignment; most people do, when they replace them
posted by thelonius at 6:45 AM on January 31, 2014

It's got nothing to do with the equipment in the trunk of your car. Either you've installed a low-quality HID bulb, as Mitheral mentions, or you've installed them incorrectly, so they're pointing too high - right into the eyes of all the other drivers on the road, who therefore think that you've got your high beams on. Either way, you're blinding other drivers and creating a hazard. You should take the car in to a shop and have them correct the alignment, and use OEM replacement bulbs.
posted by Dasein at 8:11 AM on January 31, 2014

I've seen headlamp bulbs that will clearly only work as intended when they're mounted one way around (half the bulb glass is actually mirrored) that can still be fitted in either of two orientations. Yes, this is idiotic design.
posted by flabdablet at 9:54 AM on January 31, 2014

I don't know what type of headlights you have, but I remember on one of my old cars with sealed beam headlights the replacement wasn't seated properly so one headlight was tilted up. The fix was just lift it out and carefully put it back in.
posted by ckape at 2:08 PM on January 31, 2014

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