How To: Diagnose an electrical leak in your car
How To: Diagnose an electrical leak in your car
4:19

How To: Diagnose an electrical leak in your car

Car Culture
Well I can hardly think of anything more frustrating than a battery in your car that's dead every morning. And the frustration part is, what's causing it? The so-called parasitic loss, or phantom draw is frustrating to track down, because unless it's caused by something visible like a light bulb, how do you spot it? But I can show you some simple tips to track it down very quickly that you're likely gonna need at some point with today's heavily electrical and electronic cars. [MUSIC] Now, the first thing you wanna do before you start this process Make sure you've got a good battery safe, good charge. And since the car has been crapping out, I bet you've already infested in a battery charger. So hook it up over night. Let it charge up the battery before we get started and you should see good numbers on the display. Next, make sure the car is not actually drawing any power. Obviously it's got to be switched off The key is out, doors are closed and no lights are on. And some of those take a moment because of internal timers. Now, set up your meter. For a test like this, they want you to put the black cable that came with it into the port called COM. And the red test lead goes in the one that'll typically say 10 Amps, 10A or 10A DC, like this one. So that's the kinda test we're gonna be doing. Then, turn your meter on and go to the 10 Amps DC position on its dial. Now it's time to attach your meter. If you've gotta charger connected to the battery, now is the time you wanna pull it off. Now you want to put your positive terminal back on, make sure the car has that on. And tighten so positive is back on. Negative stays off. Then your meter is put in line between the cable for negative and the terminal for negative. Now most clips are only big enough to go around your cable. Getting it around that terminal on the battery is asking a lot. So just hold your connector there. And take a look at the reading on the meter. [MUSIC] What you wanna see is a number that is in the milliamps, a very low number. 30, 40, maybe 50 at most. It's okay, the battery is not gonna die very soon with that little bit of trickle. But when I see what I've got here, nearly 2.5 amps, that's a dramatically bigger draw and that's gonna kill my battery overnight. Right. [MUSIC] Now that I've verified I've got a draw, I need to go into the car to look for it but still see the meter operating. So get some kind of a clamp, like one of these, and make sure you've got both of your leads from your meter connected to the battery so you can be hands free. This is important, when you've got you meter hooked up like this, do not start the car, turn on the head lights or do anything like that. Leave the car dead or you're gonna fry that That meter and who knows what else. Put this meter in the windshield when you can see it and then let's go around the drivers door. Okay, now with our meter setup where I can see it up on the windshield, I go down to the fuse box. And by the way, some cars have several scattered around the vehicle. Check the owners manual. Luckily here on the Boxster we just have one to deal with. Now it's just a very simple process. Just start pulling each fuse one at a time, look at the meter see if it drops your draw down where it should be. And if not, put the fuse back in, go on to the next one. It's tedious but it's easy and it costs you nothing. [MUSIC] Okay I've been pulling fuses for a few minutes here getting no results. Then all the sudden I found one that did. Look at that nice low current reading. That's C3 on this car. SO I grab the little fuse map and see what it says and it tells me that its basically interior locking and lights. So I've discovered the system that is doing the draw. Now from here its going to be up to you on whether you want to have it fixed or whether you think you can look around and figure out what the problem is. If you do wanna try and go further and diagnose it, there are four major areas to look at. Is there a motor that's running when it shouldn't. Is there a light staying on when it shouldn't. Is there a switch that's causing one of those to stay on when it shouldn't or is there a wire Are going to one of those things that I discovered that's frayed or damaged that's arching out against some piece of metal in the car. Now whether you're gonna fix the problem you've identified or take it to a shop and get it done, you've really accomplished two things right now with almost no effort and no cost. You've got piece of mind about what the problem really is, and secondly you've just found yourself an easy way to buy yourself some time. If you can live without the system that this fuse used to power up You can leave it out. And now your car's not gonna discharge and [UNKNOWN] the time and more money to get it fixed. [MUSIC]

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