How to test an alternator with Multimeter

Alternator is actually a generator which converts mechanical energy into electrical one. In cars we could found it near engines. Its main purpose is to charge battery all the time when vehicle is in running state for stability of battery voltage.

In case of malfunctioning of this device car’s battery may goes out of charge, turning into a serious issue for you. Don,t worry here we’ll tell you how to test an alternator with multimeter. It’s a quite simple procedure which did’nt actually requires electrical skills.

Follow these steps to check alternator with help of automotive multimeters,

Checking Battery Condition

  1. First of all turn on your multimeter, make sure that it has a charged battery.
  2. Now put black probe into com jack and red into volt-ohm terminal.
  3. Set multimeter’s range to dc 20 volts or more.
  4. For checking alternator you have to test vehicle’s battery, for this connect meter probes to battery terminals respectively.
  5. If meter is givving somewhat 12.5 to 13.5 volts that probably means that battery is in good condition, also the alternator.

Testing Realtime Alternator’s Performance.

  1. For this you’ll need another participant who will start the car, while you’ll observe readings.
  2. Now tell one of your companion to start the car to check alternator real time performance.
  3. Once the car engine had been started, observe current voltage level of battery.
  4. If it’s in between 14 to 14.8 that will indicate that aternator is in working condition.
  5. If it’s above 14.8 that means alternator is overcharging battery.
  6. Same as below 14 voltage will be indication that alternator is not charging battery.

Testing Alternator with Multimeter

There is another process to check condition of car alternator frequently applied by pro automotive electricians. If you can easily reach to your car alternator then connect red probe of multimeter to alternator positive terminal and black probe to any metal part near it, it may a bolt or other thing. You may also connect black probe with negative terminal of battery.

Now check readings on meter screen, it should be 14 or nearby to make suer that alternator is doing well. If you’re getting a low reading like 13 or more that may be due to low rpm speed, verify it by increasing engine’s rpm to 1500- 2000. Voltage level should be improved after this, if it’s still giving low volts then check alternator belt and pulley whethre they are working well or not.

There may be numerous reasons of a bad alternator’s voltage, from low rpm to belt or pulley issues. It may also due to alternator’s voltage regulator problems. If you checked everything and found them well then it’s time to replace your car’s alternator.

What are the signs of a faulty Alternator?

A malfunctioning alternator give many signs before its complete failure. For example an early battery drainage may be a sign of a weak alternator alongwith battery issues aswell. Your vehicle’s weak cranking/starting power may be also an indication for it or a dimly headlights may refer to slow performance of alternator. Any abnormal noise from engine side is also a sign to check your car’s alternator.

Another Classic method

This is an old method used by auto electricians to test alternators. In this simple method well’ll teach you how to test an alternator off the car. Connect the multimeter’s black probe with negative terminal of battery and black probe to alternator’s body after starting engine. After that turn on all electric accessories like audio systems, lights to put load on alternator.

Now check readings on multimeter that should be somewhat between -0.04 to -0.05. Give race to car engine to increase rpm and observe the change. The reading should not change abruptly, if this results in minor change of readings that’s a proof that alternator is in good position.

How a bad Alternator may effect a Car

If a car is running with a faulty alternator it may results in many harmfull affects on car. Like a bad alternator can destroy battery performance, even results to total damage. An alternator with weak or spining belt may damage other engine parts anytime in case of sudden breakage. Due to poor performance of alternator you may face a low voltage output of battery which is a risk for vehicle’s headlights, audio/video systems and other accessories.

Final Verdict

Till now you’ve learnt how to test an alternator with multimeter thoroughly. Although it’s a technical matter which may require a professional technicians but still you may do a self test easily after learning these skills and solve minor issues. We recommends you do not try make major changes by yourself if you’ve no proper trainings for it.

These self troubleshooting techniques are actually for first aid and minor faults. As sometimes even bad connections or wears and tear may lead to under performance of machinery parts.

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