What Causes Low Voltage Output On a Generator [6 Reasons]

Generators are quite popular nowadays whether at the home, office, school, and other places.

You will find them mostly being used as a backup power source in case the mains supply has a blackout.

Generators could also be used in case there is no quick access to power.

If you have worked with a generator before, one common problem that might have been detected is low voltage.

Having low voltage is not something to entertain from a generator. It is best to have it fixed in good time. 

Low voltage from a generator can lead to overheating of appliances that are drawing power from it. This is because the appliances have to draw more current to match their need for power.

More current leads to more heat.

So, what causes low voltage? And how can such be fixed? We look at all that below to help you use a generator that is working correctly.

1. The load is too high

A drop in voltage could mean that the load applied is higher than the operating capacity of the generator.

Each time the load is higher, it means the generator has to slow down thus leading to a drop in voltage. This affects all the appliances connected to it.

If you continue overloading the generator, you might end up with irreparable damage to the devices that are drawing power from it.

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Such type of fault can be rectified by ensuring you follow the rated capacity of the generator. No need to keep overloading it.

2. The generator has mechanical issues

A common mechanical failure could be the generator turbo. This would mean that the generator will not have sufficient pressure and air to operate at full capacity.

Sometimes you can come across clogged fuel filters too. This means there is no enough fuel being drawn into the engine.

In case of lack of consistent fuel supply would easily lead to voltage drop.

You can resolve such mechanical issues by having the generator go through proper maintenance to find and deal with these mechanical issues.

3. A circuit breaker is damaged

Having a circuit breaker is vital for the operation of any electrical circuit. It also applies to the generator.

When the circuit breaker is damaged, it means the devices do not get enough power even if you turn on the breaker.

Once the breaker is damaged, it limits the power supply. The solution is to have it replaced and thus boost the output power.

Use a multimeter to test the power output from a breaker first. This would help diagnose if the breaker needs replacing or not.

4. Dysfunctional capacitor

Other than the breaker, the capacitor is another important part of the generator.

The capacitor is key in regulating the voltage and inducing the generator. So, when the capacitor is damaged, then the generator will not work as well.

Before you can conclude it is the capacitor that has a problem, start by removing it for testing first.

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Do not forget to discharge it first before testing. Once discharged, use a multimeter to test its performance, you should at least + or – 5 uF of what is rated on the capacitor.

Any reading out of that range would mean the capacitor is faulty and needs replacing.

5. Check the alternator

Another part that could have a problem leading to low voltage is the alternator.

The alternator is crucial for charging the capacitor. However, when the generator has been used for long, it might get faulty. That is why you end up with a capacitor that is not always charged.

This is best diagnosed by a professional. This is because it needs the right tools to know if it is still working or not.

This video can be a good guide to follow:

YouTube video

6. Damaged AVR

AVR stands for the automatic voltage regulator. This is an important part of the generator that is used for regulating its output voltage.

As you can imagine, the generator would not have stable voltage output if the AVR is broken. That is why it should also be checked in case of low voltage.

The AVR problem can be tested by checking the circuit breaker, and wiring, or ensuring it is not out of adjustment. This one you can do as per the generator’s manufacturer instructions.

Here is how to test the generator’s AVR:

YouTube video


Why is the generator having a low voltage output?

We have discussed most of the reasons above. The most common issue would be that you have overloaded the generator and it is straining to keep up.

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Can you increase generator voltage?

Adjusting the generator throttle can help in increasing generator voltage. An increase in the RPMs means increased voltage. However, do it as per the guidelines of the manufacturer to avoid overdoing it.

What controls the generator voltage?

The conductor speed while moving through the fixed magnetic field combined with the strength of this magnetic field affects how much voltage the generator outputs.

Is it costly to repair a generator with low voltage?

It often depends on what is causing the low voltage in the first place. Sometimes it can be as simple as removing a few loads and it is all good. Or you may have to replace a large component.

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