How To Test Alternator Without Multimeter (4 Step Guide)

Familiarize yourself with the table of contents listed below before we continue and I show you how to test an alternator without a multimeter.

What you need to know about how to test an alternator without a multimeter

The alternator as you know forms part of the electrical system of all combustion engine vehicles.

It is important that when you are trying to test and see if you alternator is faulty you understand it's overall basic electrical connection.

You will need to know how it  interconnects and how you can then use this knowledge to bypass certain circuitry and isolate your problem without the need for a multimeter.

The electrical system of a vehicle consists of a battery, starter motor, the alternator and all the loads of the car.

These loads consume power in the form of direct current. They include everything from the lights in the car, windshield wiper, heating ventilation and air conditioning systems and all other engine management and electronic systems.

The alternator's role is to provide energy to these systems whilst the engine is running and at the same time recharge the battery.

As you already know, the alternator only works when the engine is running.

What can go wrong?

There are two main issues when talking about testing your alternator especially without a multimeter.

The first is that the actual alternator can be faulty.

This means that for whatever reason the mechanical force from the engine being transmitted via the pulley is not being converted into electrical energy via the electrical motor, Diode trio rectifier and integrated regulator circuit board.

In essence the car’s electrical loads will all be supplied by the chemical energy stored within the car’s battery, and as you can imagine this will not last long. Under such a circumstance it is important to get the alternator changed as soon as practical. 

Word of Caution

This method of testing the alternator is definitely not ideal at all. I would only try this on older model of cars that do not have modern electrical computers and engine control units. If you are not fully aware of your car’s specifications you really do run the risk of burning all the electrical devices in your vehicle.

My recommendation is simple – rather spend some money and get a reasonable multimeter. I would not try this method without the complete know how.

Read More:>>>> Find Top Multimeters below $50

With that being said, let’s analyze how you can actually perform this test.

Equipment You’ll Need To Know How to Test Alternator Without Multimeter

To perform the test of checking the health of your alternator without a multimeter is not difficult and all you require are a few items. These are listed below:

• Battery Cleaner to remove any corrosion;
• Safety gloves and glasses;
• Spanner

Testing Your Alternator Without A Multimeter (4 Step Guide)

Step 1: Identifying the issue

Typically when the alternator is faulty your vehicle will give you a warning light indicator that says you must check your battery. This indicator typically means that the battery is measuring a low voltage. Typically this can mean any of two things. Namely:

• The battery is damaged and needs replacement; or
• The alternator is damaged and needs replacement.

Since you are not using a multimeter, this cannot be easily determined. However with a multimeter you would read the voltage from the battery terminals whilst the vehicle was running. You typically should get between 11.4V to 12.6 V.

Without a multimeter I will show you in the following steps how you can undertake your test.

Step 2: Setup and Safety

The first step in this entire process is to switch off the vehicle. Let it cool down for a little bit, +/- 1 minute. This is so that we can ensure that the elements are relatively cool and that no electrical current will be flowing throughout the internal circuitry.

As the engine is turned off, it is time to put on your gloves and eye protection. This is an absolute must whenever working under the hood of your vehicle.

You will not believe the number of injuries that have happened that could have been prevented if people simply followed basic safety processes. I know if you are undertaking this task you are fairly comfortable working under the hood of your vehicle, however I cannot stress enough that you should never get so comfortable that you do not at least wear gloves and protective eyewear.

Lastly, it is always great practice to remove any oxidation on your battery terminals. Use a reputable battery cleaner to remove the corrosion.

Read More:>>> Testing is much easier with a Pocket Multimeter (check it out)

Step 3: Physical verification

Since we do not have a multimeter we are going to need be more vigilant in conducting a physical verification.

Start by ensuring that the pulley cable has sufficient tension and that there is no sense of it being disconnected from the shaft of the alternator.

Once that is done, glance at the alternator, look for any signs of physical damage or burn marks in the internal wiring.

Lastly what I like to do to finalize the physical verification is to ensure that the alternator has sufficiently cooled down and that there are no debris/ blockages on the air vent to the motor winding which could possible cause overheating.

Once you are satisfied that the alternator passes the physical verification test, then its onto the next step.

Step 4: Start car and switch it off

At this point before you turn on your car, loosen the negative terminal of you battery, so that you can easily remove it whilst the car is idling.

Start the car’s engine and let it idle for a minute or so. Then go forward and remove the negative terminal of the battery.

If the car turns off then you know that the alternator is defective.

Frequently Asked Questions

How do I know if it’s the alternator or regulator that is damaged?

The only way you can determine this effectively is by bypassing the voltage regulator and then starting the engine again.

If the alternator functions correctly (i.e. the engine goes on and all the vehicles loads are functioning), then the regulator is bad.

Will this test work on newer cars?

This test is not recommended for newer motor vehicles and a multimeter is still the way to go.

Does this not damage the Electrical Control Unit?

Give the internal circuitry of your car, this test can cause damage to the electrical control unit, even though it is protected by the distribution box and fuses.

 However as always caution should be taken when conducting such tests and if you are not fully comfortable always feel free to contact an electrician/mechanic near you to help you fix your vehicles issues.

Read More:>>>Learn how to test your purge valve with a multimeter

Final Thoughts on how to test an alternator without a multimeter

As you can see this hack on testing an alternator without a multimeter, is not difficult. But it can definitely be dangerous if you are not aware of the electrical wiring of your vehicle. You can fry all the components if you are not careful. Be sure if you go this route you fully understand what you are getting yourself into.