The charging system of your vehicle is a really important part for the proper functioning of the entire car. This system completely relies on the alternator. The alternator is the unit that is connected to your engine and it produces electricity when the engine is running. Let it be the simplest explanation of what alternator is all over the internet.
So, on one bad day, you can see that your alternator is only giving 13 volts. You may have heard that the majority of alternators should work between 13.7 and 14.5 volts to ensure that the battery is charging properly. Now you see that your alternator is underperforming and it may make you worry.
In short, it’s not always a problem when the alternator shows 13 volts, but, in the majority of cars, alternators should be constantly working in the higher range of voltage. So, the possibility of some problem with the charging system is really high.
In this article, I want to tell you everything I know about the cases when alternators give 13 volts or even less than that and if you should worry and do something about this.
How do you measure the voltage of the alternator?
You should know that it’s not correct to measure the voltage of the alternator by measuring the voltage in any random place in the electrical system of your vehicle. You should measure it exactly on the alternator’s terminals. For this, take your multimeter, install it to measure the DC voltage, put the black cable to the negative terminal of the alternator and the red cable to the positive terminal.
Of course, you should be doing this when the engine is running, otherwise, the alternator will not be functioning and will not be giving any voltage at all.
So, if you did everything correctly, but still see 13 volts coming out of your alternator, you may start worrying. It still doesn’t mean that the alternator is malfunctioning but you will have to inspect it thoroughly.
In some cars, 13 volts are OK
While in the majority of cars, you will expect to see at least 13.5 volts from your alternator, in some vehicles seeing 13 volts is absolutely normal. Especially after the engine has been running for some time and has already charged the battery.
Every alternator has a voltage regulator. This is a small part that regulates the voltage that the alternator produces in accordance with the need of your car at a certain moment. For example, when you turn on the AC, your alternator will need to work harder to produce a little higher voltage than usual, because the AC is quite a consuming unit in your car and the overall voltage in the system can go down.
So, the voltage regulator is in charge of the voltage that the alternator produces at the certain moment. And sometimes, this voltage can be quite low because the car doesn’t consume a lot of electricity at this moment.
How can you check if it’s normal?
Well, now you know how to measure the voltage in your alternator, so you can make some experiments. First of all, you may want to make sure that your 12-volt battery is alive and healthy. If it isn’t, there is a high chance that the alternator is malfunctioning. Because if it constantly produces 13 volts only, it will not charge the battery properly.
Also, you can do the following to check if the alternator in your vehicle is working properly:
- turn the engine on;
- activate the handbrake to avoid any accidents;
- open the hood;
- check the voltage on the alternator’s terminals;
- turn on the AC in your car, turn on the music, turn on all the lights;
- go back to the alternator and check the voltage again;
- now it has to produce a much higher voltage than it produced before;
If it still produces only 13 volts, you may say for sure that the alternator is not working properly.
Now that you know that the alternator is actually doing a bad job, we can keep on talking about the problems that can cause this issue.
Why can your alternator produce low voltage?
While you can find a dozen reasons described on the internet, I’m pretty sure that you should start with the voltage regulator. This is a small part that is attached to your alternator and it decides how your alternator should work.
Your voltage regulator can fail and, in this case, you will have two possible consequences:
- The voltage is always minimal. In this case, your alternator will still be working but its voltage will not be enough to charge the battery and to provide the car with enough electricity.
- The alternator is not working at all. If this happens, your vehicle will be relying completely on the battery. And you will have approximately two or three hours until the car completely dies.
Unfortunately, there are no DIY methods to check the voltage regulator without any professional equipment and experience. You can find some manuals on how to do that, but your findings will not be completely reliable. So, if you suspect your voltage regulator to be faulty, better plan your visit to a trusted repair shop.
The second problem that can cause the low voltage issue in your alternator is the condition of the alternator itself. In high-mileage cars, alternators may be worn-out and they may require repair or even replacement. The old alternator will not be able to produce high voltage just because it has already lost its efficiency.
Again, checking this on your own is not that easy. You can only do this if you know how to take off the alternator, disassemble it, and diagnose every part that you will find inside. For the majority of us, this means that we have to plan our visit to the dealership or to the good repair shop.
What are the consequences of low voltage from the alternator?
The consequences of the low voltage in your car’s electrical system highly depend on the type of the vehicle and the level of equipment. In older cars, the low voltage will not cause a lot of problems. But if your vehicle is equipped with a lot of up-to-date sensors, modern control modules and units, it will likely suffer when the voltage is low.
But the part that will suffer most is certainly the 12-volt battery. When your alternator produces only 13 volts, the battery will barely charge. And if this happens during one or two days, it will be more or less ok. But if this happens for a long time, the battery will lose all its juice and eventually die.
You will not notice the process because even when the battery is low, it will most likely start the engine. Only when it’s almost dead, you will notice that the cranking time is longer than usual, and the lights are dimmer. This is usually too late to try and save the battery.
Also, the malfunctioning alternator can kill some fuses in your vehicle. It means that some electrical equipment will suddenly stop working. Diagnosing this problem is not that hard – you will need an OBD2 scanner to figure out which fuse is blown. But first of all, you will need to deal with the alternator’s problems.
So, the faulty alternator that doesn’t produce the needed voltage and isn’t flexible enough to adjust to the current electricity consumption in the vehicle can actually be very harmful.
Can you repair the faulty alternator on your own?
Given the prices for labor in repair shops and especially in the dealership are very high, you may want to repair your alternator by yourself. And you may see that the voltage regulator for your model of the alternator costs just several dollars. But the problem is that installing it correctly and making sure it works properly will take a lot of effort.
Also, locating the problem and finding a way to solve this issue requires expertise and experience.
So, I don’t recommend relying on your own knowledge and experience when you need to deal with a faulty alternator. This is a very serious part of the electrical system in your vehicle, and you need to make sure that it works properly. Find a good mechanic that will not take a lot of money from you but will still ensure that the electrical system in your car is absolutely good to go.
Final thoughts
You are not likely to have a lot of problems with your alternator or the voltage regulator up until the car hits the 150,000-mile mark. But your alternator can still be damaged by water or by any mechanical impact. It’s located in the front part of the vehicle, so it will be damaged in pretty much any car front-end accident. Also, in many cars, the alternator is not covered by any splash protection, and it can be impacted by water if you suddenly drive into a deep puddle on the road.
But anyway, if you register that your alternator gives 13 volts instead of staying within the range of 13.7 to 14.5 volts, it doesn’t immediately mean that the alternator is broken. You need to follow the guidelines in this article to check the unit and to make sure it really malfunctions.