Last Updated on November 7, 2022 by Ellis Gibson (B.Sc. in Mechanical Engineering)
Your car is your pride and joy. You take care of it like it’s your baby. You wash it, you change the oil, and you make sure it’s in tip-top shape. So, when you turn the key and nothing happens, it’s devastating. You may think it’s the battery, but it could be the alternator. Here’s how to tell if the alternator is draining your battery.
So, how to tell if alternator is draining battery?
To test if your alternator is draining your battery, open the hood and start the car. While the engine is running, remove the negative cable from the battery. If the vehicle stalls or dies, the alternator is likely bad.
Let’s dig into it and see if we can figure it out.
Key Takeaway:
- It takes approximately 30 minutes for a bad alternator to drain a battery. However, there are some instances where it might take up to two hours.
- A bad alternator can drain a battery while the car is off. This is because the alternator will continue to charge the circuit, even when the car is off, which will drain the battery.
- If your alternator diode is bad, it can cause your battery to drain. This is because the diode helps to regulate the flow of electricity between the alternator and the battery. If the diode is not functioning properly, it can allow too much current to flow from the alternator to the battery, which can cause the battery to drain.
- A defective alternator diode can cause your car battery to drain when the car is off. This can prevent your car from starting.
Why would your alternator drain your battery?
There are a few reasons why your alternator may be draining your battery.
One possibility is that the alternator is not charging the battery properly. This can happen if the alternator is not working correctly or if there is a problem with the charging system.
Another possibility is that there is a problem with the battery itself. This can happen if the battery is not holding a charge or if it is shorting out.
Finally, it is also possible that there is a problem with the electrical system in your car. This can happen if there is a problem with the wiring or if there is a problem with the fuse box.
How can you tell if your alternator is draining your battery?
If your alternator is draining your battery, there are a few things you can look for.
Step-01: Checking the Battery
The first step is to check the battery. If the battery is old, it may be shorting out and causing the problem. To test this, disconnect the negative cable from the battery and leave it disconnected overnight. In the morning, try starting the vehicle. If it starts right up, the problem is most likely with the battery.
Step-02: Checking the Alternator
If the problem persists, the next step is to check the alternator. With the digital multimeter set to the 10 amp setting, touch the positive lead to the alternator clamp and the negative lead to the battery post. If the reading is over 50 milliamps, the alternator is most likely the problem.
To confirm this, disconnect the wiring harness from the alternator as well as any other wires attached. If the reading drops back down to between 25 and 50 milliamps, the alternator is most likely the problem.
If the reading does not drop, there may be a problem with the regulator in the alternator.
Step-03: Checking the Fuses
Another possibility is that there is a problem with one of the circuits in the vehicle. To test this, remove all of the fuses from the fuse box and connect the positive lead of the multimeter to the fuse box. Touch the negative lead of the multimeter to each of the fuses in turn. If the reading drops significantly when a particular fuse is removed, that fuse is most likely the problem.
How to Do a Parasitic Battery Drain Test?
Step-01:
First, you need to check your battery. Get a voltmeter and put it on the DC volts setting. Check that the battery is around 12.6 volts or above. This means that the battery is good.
Step-02:
Next, check the battery cable terminals. Make sure that there is no corrosion and that the cables are clean. This will ensure that there is a good connection between the post and the terminal.
Step-03:
Now, turn your multimeter to the amps setting. You want to make sure that the reading is below 0.5 amps. This means that there is a parasitic draw on the battery.
Step-04:
To find the source of the parasitic draw, start by pulling fuses one by one. Check the multimeter after each fuse to see if the reading has changed. The fuse that causes the reading to change is the one that is causing the parasitic draw.
Step-05:
Once you have found the fuse that is causing the parasitic draw, you need to figure out what that fuse controls. This will help you determine where the short is.
Step-06:
To fix the parasitic draw, you will need to either replace the fuse or the component that is controlled by that fuse.
What are the consequences of an alternator draining your battery?
If your alternator is draining your battery, it means that it is not providing enough power to keep the battery charged. This can lead to a number of consequences, including your car not starting, your headlights dimming, and your electronics not working.
In extreme cases, it can even damage your battery. If you think your alternator is draining your battery, you should take it to a mechanic to have it checked out.
How can you prevent your alternator from draining your battery?
There are a few things you can do to prevent your alternator from draining your battery.
- First, make sure that your alternator is charging at the correct voltage.
- Second, keep your battery clean and free of corrosion.
- Third, keep your alternator belts tight and free of debris.
- Fourth, if your alternator is overcharging, have it checked by a professional.
What are signs your alternator is going out?
There are several signs that your alternator is going out.
The first and most obvious sign is that your car won’t start. If your alternator is going bad, it won’t be able to provide the power needed to start your car.
The second sign is that your headlights will be dim. If your alternator is going out, it won’t be able to provide the power needed to keep your headlights bright.
The third sign is that your car will stall. If your alternator is going out, it won’t be able to provide the power needed to keep your car running.
Finally, if your alternator is going out, you will likely see a warning light on your dash. If you see any of these signs, it’s time to take your car to a mechanic and have them check your alternator.
How can I tell if I need a new battery or an alternator?
There are a few ways to tell if you need a new battery or an alternator.
One way is to check the voltage of the battery. If the voltage is low, then it may be time for a new battery.
Another way to tell is to start the car and then turn on the headlights. If the headlights are dim, then it may be time for a new alternator.
How can you tell alternator is bad by disconnecting battery?
In a vehicle, if the alternator is bad, you will see a voltage reading on the battery that is low, and the vehicle will not start.
To test the alternator, you can disconnect the battery cable and see if the voltage reading on the battery is the same.
If it is not, the alternator is probably bad and needs to be replaced.
Final Word
If you’re having trouble starting your car, or if it’s running a little bit slower than usual, it might be time to check your alternator. An alternator that’s not working properly can drain your battery, and eventually cause your car to stall.
There are a few easy ways to tell if your alternator is draining your battery.
First, check to see if your car’s headlights are dimming. If they are, it’s a good sign that your alternator isn’t providing enough power to keep your battery charged.
Another way to tell if your alternator is draining your battery is to listen for a clicking noise when you turn on your car. This noise is usually a sign that your alternator is failing.
If you think your alternator might be draining your battery, it’s important to have it checked out by a mechanic as soon as possible. A failing alternator can damage your battery, and it can also cause your car to stall.
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