How Does A Starter Generator Work?

A starter generator is a consolidation of two distinct engine elements that are majorly found in garden tractors, aircraft, and lawn tractors.  Its starting system is almost similar to the direct cranking electrical system. After functioning as a starter, they consist of the second series of winding that enables it to switch to a generator while the engine reaches a self-sustaining speed. 

In short, the starter elements produce the initial ignition. This starts the vehicle, and the generator keeps the voltage while the car is being operated. For better understanding, let’s discuss it one by one as follows;

Starter Generator

Steps On How Starter Generator Works

Voltage: the direct current voltage sent from the vehicles’ battery makes the starter generator start engaging.  When you switch on the ignition, the electrical connection is closed, and voltage is transmitted to the element’s starter. Afterward, the starter turns, starting the engine. Simultaneously, voltage is transferred to the spark plugs, which ignites the fuel inside the engine turbine or cylinder.

Starter:  typically, the starter part of the elements has a stator, windings, brushes, and armature. Voltage is sent to the coil, through which armature wire is connected then into the brushes. When voltage flows via a series field, a magnetic field is generated.  The voltage passes via different coil parts while changing the magnetic fields generated.

Generator:  generator parts of the starter generator elements feed voltages to all vehicle electrical components. Note that the lights, computer systems, emergency shutoff, and other electronics on the aircraft, car, or tractor need to be powered. The generator transfers the right amount of voltage to all elements while keeping enough to operate all electronics simultaneously.

Troubleshooting: starter-generator can run into problems caused by these assemblies. Since there is one coil, it can limit the vehicle’s features. Other components generate a specific amount of current; for example, standard automotive and tractors generators have cooling fans on the elements even though the starter generator is enclosed, and it can cause it to overheat. Electric flow breaks can be caused by too much wear of brushes. You thus need to troubleshoot the brushes using a voltage meter and a magnet. 

How Do I Know My Starter Is Bad?

When You Turn The Key, It Doesn’t Start

Whenever you turn the key to start your motor, but it doesn’t ignite, and you hear some clicking sound, then the starter or battery could be bad. You, therefore, need to find out what the issue is by turning your vehicle’s lights on either the interior or the headlight. If they are working, it means your battery is fine, and thus, the starter generator might be having issues, and you should have it checked by a mechanic. 

Time Is Taken To Crank

A delay for the starter to crank indicates the possibility of your starter generator going bad. Turn your lights on to rule out the probability that your battery might be having issues. If they work perfectly, there are issues with the starter. 

Noise Coming Out

If you hear a grinding noise coming out when you start, your vehicle signals out that your starter’s gears are worn out and are not working properly. Typically, it’s the kind of noise you hear when you turn the key on your vehicle that was already on.

Smoke Coming Out Of Your Vehicle Or The Starter Is Too Hot.

When you feel the starter is getting too hot quickly, it’s a strong sign that there is a problem. The voltage will drop out due to the starter getting too hot. But when you see the smoke coming out, know it’s a done deal; there is a blown and short circuit. Call for help and stop turning the key harder again.

The Pulley Of The Starter Is Rusted Or Not Moving Freely.

When the pulley doesn’t move freely on moving by your hand or looks rusted, be prepared, your starter is going bad. If the rust on the pulley has not reached the starter, you are better off. But suppose it; you should replace the starter-generator system right away.

Oil Has Soaked The Starter

Generally, your starter is located on the motor’s driver side, just below the cylinder’s left bank. Suppose your starter is drenched with engine oil; it a sign of an oil leak on top of your bad starter. Unluckily, a small problem can turn into an expensive problem if you don’t act immediately. Keep your eyes open on oil leaks, and avoid possible starter issues.

Can a starter be used as a generator?

Yes, it’s possible to use a starter motor as a generator. Nonetheless, cars nowadays no longer use generators. They use alternators that produce AC output and are later converted to DC. Moreover, alternators are affordable and lighter compared to generators.

A starter is designed for low speed and high torque. It draws a very high flow of current within a short period. Even though a starter could work as a generator, it doesn’t mean it will work well as a generator. The winding and armature are not similar to those of a generator and cannot produce minimum current in a steady-state manner. All these changes require additional hardware, whether you need the equal weight of an alternator or not.

How Do You Check If A Generator Is Charging?

It’s essential to check if your generator is charging before you go on with your daily chores using a voltmeter. To check, you have to measure the voltage across the batter. When the engine is off, it should be 12.6 volts, and when its speed up, the voltage is supposed to increase to around 14 volts. When there is an increase, the generator is working and charging the battery.

However, when the voltmeter doesn’t increase with the engine running, you need to confirm first if the generator brushes are worn out. If possible, apply a little pressure to the brushes as the engine runs and check if the gen lights go out or the voltmeter reading increases. When that happens, the brushes are worn out to the point that they don’t put enough pressure on the commutators.

What Happens If You Don’t Polarize A Generator?

Polarizing your generator is very important, and if you don’t, it will get damaged together with the motor. Other switches that are on the same circuit will harm your device. So, the generator will not only get impaired, but contacts and anything plugged into it as well.

Normally generators store magnetism in their pole pieces, which helps them remember how the current flows. Usually, the residue magnetism will be sufficient to allow the generator to function correctly. If the generator is removed from its housing, there are chances that the stored magnetism will dissipate gradually. That’s why it’s advisable to always polarize your generator correctly before introducing it to an electrical system. 

How To Polarize A 12V Generator

You will need; 2 alligator clips, an insulated screwdriver or socket set, jumper wire, i4 or 16 gauges, and an electrical tape to start the process of polarizing a 12V generator. You can install your device on either positive or negative grounds. However, you must understand the electrical system polarity. You should then follow the steps below: 

Step 1: Remove The Fan Belt

First, you need to remove the fan belt if the generator is part of the machine. Use your hand, the socket set, or screwdriver to loosen the sway arm holding the fan belt and remove it. Keep the fan belt, bolts, and screws in a safe place where you can see. Better yet, get a magnetic wrist band designed to hold small accessories like nails, screws, etc., as it will make your work easier.

Step 2: Fashion A Wire

Take your two alligator clips plus your 14 0r 16-gauge jumper wire and fashion it long enough to reach from the generator to the battery. Ensure no part of the wire is exposed using an electric tap since this can start a fire or electrical shock. You need to take your time and cover every inch using electrical tape.

Step 3: Attach The Jumper

The terminal labeled with an “a” on your generator stands for armature terminal and is where you should attach the jumper wire.

Step 4: Be Sure With Your Polarity System Before Proceeding

Very gently brush the positive (+) terminal on the battery with the other side of your wire. It will produce few sparks, and you need to be careful to avoid leaving it in contact for an extended period as this damages your generator. The process will restore the stored magnetism within the generator, enabling the right polarity current to flow when it is powered.

N/B: The first three steps are compatible with either type of system. However, the fourth one varies depending on if you have a negative or positive ground system. You need to check the manufacturing manuals before proceeding if you have doubts. 


Starter generators play a significant role when it comes to motors etc., and you need to ensure that it’s functioning to its standards. Please make sure it is charging perfectly and no oil leaks. Besides, polarize it whenever necessary. Be aware of the possible problems associated with the starter generator and how you can solve them to avoid further expenses due to negligence.

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