46 votes
Accepted

Car won't start, horn won't honk, headlights won't come on, what could cause this?

The symptoms all point to a faulty battery, and an incorrect test result for the Autozone battery test. Starting with this: Hitting brakes: Brake lights come on and interior lights dim: a good ...
Hobbes's user avatar
  • 4,412
34 votes
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Do matching (left/right) lights often burn out within a short time period of each other? If so, why?

No, the salesman was spot on. If you think about it, bulbs are designed to last about the same amount of time. If they are installed in pairs, then the secondary light which matches the first will ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
15 votes

Car won't start, horn won't honk, headlights won't come on, what could cause this?

All symptoms point to a dead battery, but as you have already attempted to rule that out, the next thing I'd check would be bad connections or cables. Turn on the headlights or something else that ...
Niko Kiirala's user avatar
14 votes

How to upgrade a motorcycle battery to a bigger AH battery?

Sure you could put a bigger battery in .What may happen is that the total proposed draw is too much for the dynamo and it will go flat.Even if it does not go flat because your appliance usage patterns ...
Autistic's user avatar
  • 2,083
13 votes
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Why are H4 LED headlights not designed correctly?

I think you hit it. Cost, most of the LED headlights are made to just pack as many LED as possible into the H4 package as possible, but a small percentage of them are actually designed to mimic the H4 ...
Paul Dufresne's user avatar
10 votes
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What is this extra light on my headlights?

According to this that extra space is for the integrated fog light, which is probably where the fog light would be if you didn't have the separate fog light.
BillDOe's user avatar
  • 1,512
7 votes
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Is it a cause for concern if one headlight beam points lower than the other

I would say the two peaks should be at the same height. In the UK, beam alignment is part of the annual MOT roadworthyness test, and the government publish a guide as to how to set them up: https://...
Nick C's user avatar
  • 28.7k
7 votes

Weird headlight issue!

Each bulb usually has 2 filaments in it, one for low beam and one for high beam. One possibility is that your driver's side bulb has a broken high beam filament and the passenger side has a broken ...
HandyHowie's user avatar
  • 25.2k
7 votes

Do matching (left/right) lights often burn out within a short time period of each other? If so, why?

Lightbulb failure is a random event, which is not pre-set to happen after X hours of service or before a certain date. It is provoked by stress from vibration, repeated heating up and cooling down and ...
Dmitry Grigoryev's user avatar
6 votes

Single headlight does not come on but is not burnt out

Sounds like the bulb socket is corroded. You could try spraying it with contact cleaner, or trim an emery board to fit and giving a couple of passes with that to remove the corrosion. With any ...
TMN's user avatar
  • 2,311
6 votes
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low beam does not work, daytime running and high beam do

Most vehicles not using an LED headlight have multiple filaments in the bulb. These frequently do burn out independently. Low beam is also the most used filament, and likely to burn out first. Given ...
Leliel's user avatar
  • 583
6 votes

Are expensive high-brightness 55W headlight bulbs worth the investment?

I think there might be a regulatory component that effects stated brightness I found in CFR (Code of Federal Regulations) 49 The maximum wattage at 12.8 volts (design voltage): 65 watts on upper ...
DucatiKiller's user avatar
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6 votes
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Head light bulbs

If the bulb in question is the same fitment as the original (is just a higher wattage or whatever), then it should cause no issues with the wiring. I believe the main differences can be linked back to ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
5 votes
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How to upgrade a motorcycle battery to a bigger AH battery?

As Autistic and Chenmunka say, if you want to increase the electrical power you're using (by having a higher-rated headlamp), you'll need to generate more power - by having a bigger alternator or ...
Nick C's user avatar
  • 28.7k
5 votes
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Are there any (legal) ways to increase halogen headlight brightness?

It is possible that the adjustment is not correct, i.e. the lights are still shining too steep down though the knob is set to 0. Though you can test this on your own, shops will do this with more ...
sweber's user avatar
  • 7,057
5 votes

Sealing / effectively preserving restored headlights

The best way to keep them looking good is to utilize clear spray lacquer which is is not affected by UV. UV light is what causes the cloudiness in the first place. By spraying the clearcoat on there, ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
5 votes
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How to fix 2007 Mercedes SLK daytime running lights?

After hours of tracing cables, removing panels and taking apart more of the car than I'd like to admit, I figured the issue out. Apparently there's a cable for control current (or something like that)....
Kallja's user avatar
  • 251
5 votes

How important is bulb grease when changing low-beam or high-beam headlights?

No, you don't "really need" it. However, the purpose of the grease is to keep out moisture that can degrade the connection and the bulb's performance. So if you see any signs of corrosion when you ...
dlu's user avatar
  • 14.5k
5 votes
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How important is bulb grease when changing low-beam or high-beam headlights?

It depends. What you are referring to is dielectric grease. It doesn't conduct electricity so it is safe to use on electrical connectors. Modern vehicle assembly lines don't grease bulbs because the ...
DizzyFool's user avatar
  • 1,571
5 votes
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Why do the headlights of supercars looking flashing on video

They flash because that's how their brightness is altered. Rather than use a large resistor to vary the current through the LEDs, they are flashed on and off faster than your eye can detect. When they ...
cdunn's user avatar
  • 9,296
5 votes
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Is this headlight cover corrupted? (Small cracks from an angle)

Everyday driving puts small scratches and chips in the lens. That along with the impact of UV light from the sun distorts the light beam as it passes through the lens. The light gets scattered and ...
mikes's user avatar
  • 19.9k
5 votes

Is this headlight cover corrupted? (Small cracks from an angle)

This answer pretty much coincides with @mikes' answer, with a little different understanding of what's best. The pits/marks on your headlight covers can easily be taken care of with a polishing kit ...
Pᴀᴜʟsᴛᴇʀ2's user avatar
4 votes

Single headlight does not come on but is not burnt out

The filament could be broken in one spot, and moving the bulb could be shaking it so the broken section makes contact again and it illuminates. I've seen this before with household light bulbs. I'll ...
JPhi1618's user avatar
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4 votes
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Why would headlights stop working after turning over

Turns out what went wrong was my car was turning on the brights (highs) when I would go to unlock it, and the regular (lows) headlights were never working. I thought the car was turning on the lows ...
DeepDeadpool's user avatar
4 votes
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How to diagnose undervolt in electrical system

There are several things you can look for: Complete paths Electricity requires a complete path from positive to negative. In a car with that kind of age, I would be checking that you don't have bad ...
cdunn's user avatar
  • 9,296
4 votes

Low beams don't work but the high beams work in a 2002 Toyota Tacoma

According to the wiring diagram the power is supplied to the bulbs through the relay and then one fuse for each bulb. If the high beams work then the relay and fuses are working. The lights are ...
Fred Wilson's user avatar
  • 11.6k
4 votes

High beams work, low beams do not. What is wrong with headlight?

There are a few things that could be problems: Confirm that the bulbs are good. I've seen it happen more than once that one bulb burns out and you don't notice, then the second bulb burns out and ...
dlu's user avatar
  • 14.5k
4 votes

How does color temperature influence headlight performance?

The color of light, expressed in degrees Kelvins (K). The sun is about 5800 K. This is called a "temperature," because the hotter a flame or a lamp filament gets, the more it changes from a warm ...
Old_Fossil's user avatar
  • 3,962

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