Today I will teach you the easiest way to troubleshoot a vehicle that has a battery, which drains down overnight or over a few days of not using the vehicle.

Let’s get started the first thing you’re going to do is rule out the battery as being the cause of your problem.

As batteries get older, the place could start to short out causing the battery to drain down.

When it sits for hours at a time, so the thing to do is when you’re done driving the vehicle for the day.

The alternator was running charging up the battery, you’re going to disconnect the negative from the battery, and you’re going to leave it disconnected overnight.

In the morning when you go to connect this back on to the battery, If the vehicle starts right up and you don’t have the problem with the battery being drained down anymore, then clearly there is something in the vehicle that is draining the battery down.

If you still have the same problem where the battery is not strong enough to turn the engine over then definitely replace your battery.

When the wires initially connected to the battery, you’re going to notice a spark and the reason for that is a surge of current going into the vehicle charging up capacitors, powering circuit boards.

Usually that current is under one amp, usually 300 to 750 milliamp.

Then after a set duration maybe around 15 seconds, 20 seconds, that current should drop to a level between 25 to 50 mA. If the current being drained from the battery is well above 50 mA then the battery can drain down over time from sitting.

When you do this test, I’m about to tell you make sure that there’s no light on your hood. If there is a light on your hood, remove the bulb because that’s going to interfere with this test.

Using an inexpensive digital meter. You can pick these up at Harbor Freight. They’re very cheap they’re around $5.

You going to set the meter to DC current, I have it on 10 amps and the 10 amps setting.

I’m going to disconnect this clamp again, I’m just going to show you how the current flows in going to take the positive, put it on the clamp.

I’m going to touch one end and you’re going to check 0.5 would be a half of an amp 0.01 would be 10 milliamps.

You could tell right here, that’s 720, or so that’s 530, 160 and you can note it dropping all the way back. We’re at 30 25 to 30 milliamps.

That’s what you should check when you check your battery.

If you have a digital multimeter, before I connect the digital meter back up again to perform the test. What you’re going to do is expose all your fuses, you have a fuse compartment under your hood as well as under the dash.

Always start on the 10 amp setting on multimetere. If you start on a 200 milliamp setting, you’re going to blow the fuse, so leave it on a 10 amp to make life easy.

You’re going to take a jumper wire. You connect that over there and the other one. You can take another jumper wire that has a wide enough jaw to clamp on to the post.

We’re going to touch it again. We’re going to let it settle down right now.

It’s at 160 milliamp and we’re down probably around 25 not even 20 mili-amps. What you would do is while this is connected and you can have an assistant watch the meter.

Check the reading of a 100 milliamps or 200 milliamps you’re going to go to each one of the fuses and pull them one at a time and check the meter.

If the meter drops way down to where it should be between right circuits and then you can inspect just that circuit to find out where the problem is.

Go to every single one as well as under the dash and you will find the problem. If the reading on the meter does not drop from that higher than normal current reading.

Many times in the past, I’ve check a faulty regulator in the alternator caused the problem of draining down the battery.

You can go over to the alternator, pull the wiring harness off the alternator, as well as any other wires attached and take a look at the reading.

If you note the reading go back down to where it should be between 25 and 50 mA, then you’re gonna know your alternator is the problem.

Just have an assistant checking the meter, while you’re pulling fuses and if none of the fuses work check the alternator.

There is one more thing I would like to tell you when removing fuses from the inside of the vehicle, the door will most likely be open make sure you push in the button on the door jamb or have an assistant.

Do so while you’re removing the fuses if you do not push this button the interior light will be on and you will not know when you found the correct circuit.

When you pull out the fuse because the light will be on inside the vehicle drawing current from the battery.

If you wish to share your thoughts on this matter, feel free to leave a comment below.


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