How to test an alternator without a voltmeter ?
Every problem in a car can happen anytime and anywhere, especially if the car maintenance is done with irregular periods. One of the problems that usually occur in a car is the battery runs out due to an alternator failure.
Suppose this problem occurs in a relatively safe condition. In that case, you should test the alternator with suitable and safer tools such as using voltmeter to test car battery first or a suitable car charging system inspection tool.
If you run out of idea on how to test the alternator, you may conduct some steps below to ensure the alternator is good or in bad condition.
- Check the charging system light: Most vehicles have a charging system light on the dashboard that indicates whether the alternator is functioning properly. If the light is on when the engine is running, it could be a sign that the alternator is not working correctly.
- Test the battery: If the alternator is not charging the battery, the battery may not have enough power to start the vehicle. Try starting the vehicle and see if it has enough power to turn over. If the battery is dead, try jump-starting the vehicle and see if it stays running.
- Check the belts: If the alternator belt is loose or broken, it could be the cause of the problem. Check the belts and see if they are in good condition.
- Listen for strange noises: If the alternator is failing, it may make strange noises. Listen for any unusual sounds coming from the alternator while the vehicle is running.
If all the check list above are fine and good but you still want to know if the alternator can normally work while you don't have a voltmeter, you may bring up this alternator test. But remember, it can be difficult to accurately diagnose the condition of the alternator without the use of proper testing equipment. So, here are how to test an alternator without a voltmeter.
1. Do an alternator magnetic test
Because the alternator works based on electromagnetic, we can do an alternator magnetic test to test an alternator without a voltmeter. This magnetic test is used to check the effect of the electromagnet produced from the rotor and stator components inside the alternator.
As we know, if any electric current flows through the coil, it produces magnetic field. Any metal things near the magnet will pull into the magnetic source. In the alternator, the rotor coil is related to the pulley. In contrast, the stator coil is related to the body of the alternator.
Suppose the magnetic effect won't work inside the alternator. In that case, it indicates the rotor coil or the stator coil has broken or failed to let the electric current flow.
To conduct an alternator magnetic test, we need something made from metal, such as a wrench or screwdriver. Caution, if the alternator was challenging to reach inside the engine (for example, the location is below the engine and its hard to reach), it is better to not do this magnetic test.
Here's an alternator magnetic test. Do it very carefully.
A. Magnetic test on alternator's rotor coil
- Turn ON your ignition key (don't run the engine, only turn it into ON position).
- Look for the alternator pulley.
- Put your metal wrench close to the alternator pulley.
- If the wrench sticks to the pulley, then the electromagnetic from the rotor coil works well.
- If the wrench won't stick to the pulley, the rotor coil has broken and failed to produce an electromagnet.
B. Magnetic test on alternator stator coil
- Start your engine and let it run until it reaches an idling rpm.
- Look for the body part of the alternator.
- Put your metal wrench closer to the alternator body (do it very carefully !!)
- If the wrench sticks to the alternator body, then the electromagnetic from the stator coil works well.
- If the wrench won't stick to the alternator body, the stator coil has broken and failed to produce an electromagnet.
What this mean?
If the magnetic test works well, it indicates that the coils (on rotor and startor) are in good condition. The electric current flows from the battery to the coils. It means your alternator is fine. If the tests are failed, it indicates that the alternator is in bad condition.
Read also :- How to test car battery with voltmeter
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2. Do an Alternator voltage and current test
The next step about how to test an alternator without a voltmeter is to do an alternator voltage and current test. This test is to ensure that the alternator produces voltage and electric current to the engine electrical components.
The alternator works when the engine is running. It produces electric currents to power all the electrical components and to recharge the battery. Suppose the electric currents don't come up from the alternator to power all-electric components. In that case, your car engine will stop running.
Most car charging systems use the positive battery as the doorway of electric currents flow so the charging process can be done. That's why the alternator voltage is always higher than the battery voltage. And what we do here is to pull off the positive terminal cable from the battery when the engine is running.
How to test alternator by disconnecting battery?
Below is how to test alternator by disconnecting battery that we can do:
- Start your engine and let it run until it reaches an idling rpm.
- Turn off all electric system in your car (AC, Headlight, Audio Video, etc).
- Loosen the nut on the positive battery cable (be careful and prevent the wrench from contacting the battery bracket, car frame, body, or the negative terminal).
- Pull the positive cable from the battery terminal and hold it carefully.
- Pay attention to the engine.
- If the engine stops, it indicates that the alternator was failed to produce an electrical current for the car.
- If the engine is still running, it indicates that the alternator works well.
- Turn the engine OFF, then detach the negative battery.
- Reconnect the positive battery cable first, tighten up, then do the same with the negative cable.
Caution:
It's a risky test, do it with your own risks. Here are some things that we must consider when testing alternator by disconnecting battery.
- Be careful when connect or disconnect the positive cable. Don't be short because the charging fuse will blow if a short circuit happens.
- Please do it for emergency test only, don't repeatedly do.
- Read your car owner's manual for disconnecting the battery because some car models need extra action after it.