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testing your alternator

Have you ever experienced a stalling engine, accessory malfunction, battery warning light or dimming headlights? In most cases, either the car battery or alternator is faulty.

 An alternator supplies the vehicle with DC power and when it comes to the charging system of a vehicle, the alternator is of significance and goes further to charge the car battery while powered by the engine.

There are various ways to test your alternator.

Testing your alternator by disconnecting the battery can be unsafe. It was a method used long ago. However, it is unsafe considering this action will cause the alternator to put out maximum work resulting in excessive heat, which will shorten the life of the alternator or even damage it. Disconnecting the battery to test the alternator also results in more voltage production of 150 volts spikes, damaging electronic equipment since the cushion which is the battery is absent 

Safety precaution is mandatory in every method stated, and one should also follow the rules provided in the vehicle manual concerning alternator testing.

Safe ways to test an alternator include ...

Using a Multimeter

A multimeter is a handheld device used to measure or test various electrical properties. 

When using a multimeter to test your alternator, the following steps come in handy:

  • Get a high-quality multimeter.
  • Connect the multimeter prongs to the terminals of the battery, positive to positive and negative to negative while the engine is off and the car battery is fully charged.  
  • With the vehicle off and all accessories, take a reading. The reading of the voltage should be approximately 12.7 volts (12.5 to 12.8 volts). 
  • When the engine is on, the reading should be around 14 volts.
  • When the accessories are on, the voltage reading should be 13 or more. If not, this may imply that the alternator is not charging the battery effectively.
  • In the situation that everything is off, the reading should be around 12.8 volts.


Using a Rust-free Screwdriver (Magnetic Test)

When using a rust-free screwdriver, one should observe safety by wearing insulating gloves, and you should not be wearing hanging clothing or leaving your hair hanging.

Hold the tip of the screwdriver near the bolt holding the alternator pulley wheel. There should be no pull. 

Afterwards, use the screwdriver to touch the pulley bolt when the car or truck's ignition and dashboard lights are on, but the vehicle has not started. There should be a strong magnetic pull on the screwdriver. Failure to observe any magnetic pull shows that either the regulator or alternator is faulty.


Observing Your Vehicle’s Internal and External lights

Dashboard lights flickering or the headlight dimming may signify a faulty alternator. 

Finally, another method is to take the battery and alternator to a dealership or auto parts store where they can use proper load testers to determine if your battery and alternator are functioning effectively. One can also carry out a “full-filled” test.

Alternators are of significance to running your car or truck, and knowing the above methods can come in handy in case of a quick diagnosis.  


Written by:
#MenWhoBlog MemberBlogging GuruThought Leader

James' passion for exploration and sense of duty to his community extends beyond himself. This means he is dedicated to providing a positive role model for other men and especially younger guys that need support so that they can thrive and be future positive contributors to society. This includes sharing wisdom, ideas, tips, and advice on subjects that all men should be familiar with, including: family travel, men's health, relationships, DIY advice for home and yard, car care, food, drinks, and technology. Additionally, he's a travel advisor and a leading men's travel influencer who has been featured in media ranging from New York Times to the Chicago Tribune, and LA Times. He's also been cited by LA Weekly "Top Travel Bloggers To Watch 2023" and featured by Muck Rack: "Top 10 Outdoor Journalists for 2022".

He and his wife Heather live in St Joseph, Michigan - across the lake from Chicago.