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Does My Car Have a Bad Fuse Or Bad Bulb

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Created on: 2019-12-02

When the lights go out on your vehicle, which do you check first: fuse, or bulb? this 1A Auto video shows you how to check for a bad fuse, or a bad bulb

  1. step 1 :Checking the Fuses
    • If more than one light is out, that suggests a fuse problem
    • Locate the circuit for the problem light using the diagram in the fuse box
    • Connect a test light to the ground terminal of the battery
    • Test each side of the fuse to check for a break
    • Replace the fuse with one of the same style and rating
  2. step 2 :Checking the Bulbs
    • If only one light is out, it's most likely the bulb
    • Remove the bulb from the housing
    • Check the bulb for burnt spots or broken filament
    • Install a new bulb of the same type
    • Test the light

What the heck is this guy's problem behind me? What?

Hey, buddy. You got some lights out.

All right. Thanks buddy. Maybe I should check that out.

Only my driver's side running lights don't work. What the...

Okay, so we have our headlights on. You can see that the marker light inside the bumper right here is working. The marker light here, which is also a directional, is working. We can come across. Come over to the driver side. The marker light inside the directional assembly is not working, and also the bumper marker light is not working inside the assembly. So we're going to go along to the back. We're going to check the back as well, because I believe that the left rear tail lamp is out. Okay, so we've got the left rear. That's not on, but the right rear is.

So it seems to me that the whole passenger side running lights are working, but the driver side are not. So that, kind of, leads me to believe that it's probably not a bulb. I'm not going to rule it out yet, because we have to do a little bit of diagnosing. So let's have some fun.

Okay, so we've got ourselves a nice, basic test light. We're going to come to our under-the-hood fuse box. Lift this up. Now what we're going to do is we're going to take a look for something that says "Left side running lights," or "Tail lights," or "Plate light," or something like that. You just read right down the chart here, okay? Just a quick skim. Okay, here we go. Number 17. Grab my little light. Right there, we've got left side tail light, license plate, and parking lamp. That's where we've got an issue. And it should be a 15 amp fuse. So we're looking for number 17.

We'll come up on here, take a look at all these little M's. Looking for M17. Okay, here's M17 right there. It's right on the side of this nice big one, the very bottom. So we've got the big one. We'll come over here. This 15 amp fuse should be the one for the left side.

I'm going to hook this up to the negative, because I'm going to be checking for power, okay? So I'm going to connect it to the ground. I'm going to make sure that it works real quick. We're going to watch for a little light. That lets us know that it's working.

Now, I'm going to turn on the lights, so it's going to be trying to send power to the lights. Here we are. This is our number 17, 15 amp fuse. I've got power on one side. No power on the other side. Okay, let's just check this one right here. We've got power and power. That means that this fuse is working. Power, no power. Let's pull this fuse and take a look at it.

Okay, so I'm just going to turn off the lights real quick. Come over here. I'm just going to grab this fuse. Give it a little tug. Let's take a look. Oh, yeah. Look at that. You can see right up inside that plastic that those two little ends right there...those are actually supposed to be connected. This fuse right here is cooked, blown. This tells us what size we need. We need a 15 amp, and this is a mini.

We grabbed another 15 amp fuse. You can tell that this one is not blown, and this one right here is. We slide that right into the slot that we removed the broken one from. Turn on some lights here. We'll take a look. Awesome. Go double check the rear real quick. Oh, yeah. Perfect. Easy fix.

Okay, so we found a bad fuse that was affecting the left side running lights circuit for the vehicle. That kind of made it so we didn't have to worry about checking the bulbs, because once we fixed that fuse, they all work.

Okay, so we saw how an electrical circuit worked, right? We checked that fuse. We saw that it was bad. It made it so the whole one side of the vehicle wasn't working. We didn't have tail lights on the left rear or the left front, so we were trying to figure out what's up with that. We found a bad fuse.

Sometimes you have a different situation, where you might have your brake lights on. Hey Len, can you put on the brakes?

Oh, sure.

All right. So, we've got our driver's side brake light on. We've got our upper, or third brake light. That works. But for some reason, this passenger's side isn't working. The point I'm trying to make is that the other two brake lights do work, and this one does not. So that leads me to believe that it's probably not a circuit issue. It's more than likely a bulb issue. So let's go ahead and check that.

All right, Len. Good job.

Hey, no problem.

All right. So now we need to get to the bulb. So, to do that, we need to remove your lens assembly from the vehicle. Okay. So if this was up inside the vehicle, this is what we'll be looking at. You have your reverse, directional, and then, of course, the running light/brake light. Just looking at this bulb, I can see that it's pretty dark. It's definitely burnt. So I'm going to grab another bulb.

The bulb for this application is 3157, and let's see if it works. If it does, then we know that it's the bulb for sure. If it doesn't, we'll have to continue diagnosing.

Okay. So, as you can tell, the original bulb is very dark and burnt. Here's our brand new bulb, same number, 3157 for this application. Let's give it a try.

Okay, so let's try this bulb. Let's put it in here. Hey, Len, can you step on the brake?

Sure. Whew.

All right, works. Thank you.


Okay. So we're super happy everything works. We've got running lights. We've got brake lights. And you know the difference between checking for a bulb or a fuse issue. Any other questions leave it in the comments section below.

Thanks for watching. Visit 1AAuto.com for quality auto parts shipped to your door, the place for DIY auto repair. And if you enjoyed this video, please click the subscribe button.

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