How to Test an Alternator (Easy Guide)

How to Test an Alternator. An alternator is a crucial component in your car and it cannot work properly if your car alternator is not working well. Due to the fact, it needs to be in a good condition when you need a smooth start of your car and also need to get all functions up and running without any disturbances.

No matter, if you have a new battery in your car or you have a fit engine, you will need to keep the alternator in its best form to make sure you will be getting sufficient push for your car while starting it or running the car accessories without any break.

You have to make sure the alternator is working well to keep your car battery charged in a way that it will not be overcharged or undercharged at any point. In case you are having troubles when starting your car,you may have to think about two conditions one could the condition when your car battery is not working well and you will have to check, recharge or replace it, secondly your car alternator might have some issues that may be disturbing the overall charging process of your car battery.

So, you will need to check these two things when your car sounds grumpy when you try to start it up, i.e the car battery and the car alternator. All you will need is to have a manual multimeter and join it using the two leads with the two terminals of your car battery. This will let you know the charge in your battery.

For this, you have to set your multimeter to the 20 DVC because the car battery has a 12 V capacity, so the reading will be around 12.6 volts when your engine is off. That means your battery is in a good condition and no need to proceed to check it. Now move on to check if the alternator is charging it with the desired voltage.

Start your engine and see what reading you will get on the multimeter, it should be around 14 or 14.2. In case you are getting high above 14 or below it, then the alternator is either overcharging or undercharging the battery and has a fault in it.

Another thing that you need to check is if there is any significant change in the voltage shown on the multimeter when we put on the load on the battery by turning on the headlights, the radio or the fan.

If you turn all things on and the voltage still stays within the 13 volts and don’t fall or rise significantly, it means that it is working okay. In case the voltage falls far below the 13 points or 12.7 points which are the optimum limit, you will need to check the current draw within the system.

Next, you should be checking the battery connections and the alternator wires connected to the battery. This should be made sure because if you have some damaged wires or bad connection, you will not be getting the full voltage when the alternator starts.

Additionally, you must check if the alternator belt is in its best form and tight because, without this, the alternator will not be working the way you need.

After that, you can check the current draw from both terminals. Firstly, you will need to connect the black lead of the multimeter to the negative terminal and the red one to the alternator case, turn on some accessories, raise the RPM to 1500 and see the reading. If it is around 0.05 or something, it is okay, but if you have around 1 or 2 at the multimeter, then there is a problem in the system.

If it comes as 1, you will need to touch the lead with the alternator bracket, if you see significant drop or changes in the reading, there have to be some issues with the alternator and the bracket connection. If that is not the case, you can check through the engine block by touching the lead to the bare engine side to see if there is any significant drop in the voltage.

After this check is complete and you have found the connection issues, clean the connections to get them fixed.

After that, if no issues are found, make sure to check through the positive terminal you will have to connect the red with the positive and take the black lead and attach it to the B plus post of the alternator if you get readings at or around 0.3 or below it, then it is good.

In case there is a significant draw when you have accessories on, and engine on with 1500 RPM setting, you will need clear the connections and the problems will be fixed.

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