The generator not putting out full power

Nothing can be more frustrating than seeing your generator running but not putting out full power. If you’ve been without power for an extended period, these tips can help ensure your generator runs at peak performance and not leave you in the dark.

#1 The Generator Output Voltage is Not Correct

One of the most common reasons associated with low output from any generator is the incorrect generator voltage.

Various Faults encountered and Reasons

  1. No voltage on any one of the receptacles due to faulty GFCI or the receptacle itself, bad connection, or break in wiring to the receptacle.
  2. Half the normal voltage is due to a faulty bridge rectifier or the rectifier lead wire connections, a high resistance connection, or a bad voltage regulator.
  3. Less than Half to three-quarter voltage due to the blown capacitor, misadjusted or faulty AVR.
  4. Only 8 to 12 V on all receptacles due to probable fault in the rotor excitation circuit or a short circuit in the stator winding.
  5. Fluctuation in the terminal voltage due to low rotor or stator winding resistance to ground, worn out rotor shaft bearing, misadjusted AVR stability potentiometer or faulty AVR.
  6. Excessive voltage drop on the addition of the loads due to excessive loads, low power factor loads drawing high currents causing low generator output voltage, open stator winding, issues in engine governor, defective diodes, misadjusted or faulty AVR, and poor engine performance.
  7. Continuous low voltage under normal load conditions due to faulty rotor winding, excessive engine speed droop, faulty rotor diodes, high power cord resistance, faulty AVR sensing or power circuit, or the AVR itself.

We have dealt with the reasons and troubleshooting for all these issues in detail in our article “Generator Not Putting Out Correct Voltage

#2 Imbalance in Loads

While this is not exactly a case of a generator not putting out its rated electric power, but, you are not utilizing its entire capacity to produce power due to an imbalance in the load distribution between circuits in your house.

Let us consider an example. Suppose you have a 6 kW generator that can produce 25A at 240V or 25A@120V in each of the 120V circuits, equivalent to 50A@120V, if the loads are balanced. If the loads in the circuits in your house wiring are L1 = 35A and L2 = 15A, L1 will be able to supply only 25A, beyond which it will trip out. To run the generator, you will be forced to switch off loads consuming 10A on the L1 circuit. Hence you end up utilizing only 40A, which translates to 4.8KW.

You need to rebalance the load between your circuits or go for a larger generator.

#3 The Stator is Damaged

The stator is an important component in all portable generators, and its malfunction can cause a generator not to put out full power. Alternators come in two types: brushed and brushless. A magnetically charged rotor produces a rotating magnetic field that links with the fixed stator windings producing electricity. As pointed out in the first section on incorrect voltage, the open circuit, short circuit, or fault to the ground can result in improper power output from the generator.

Testing a stator can be a time-consuming job but can give answers to a number of generator issues. To check the brushless generator stator, remove the wires connecting the stator to the electrical panel. Consult your owner’s manual for information on the wires’ function and the normal resistance rating for each stator coil.

Three tests can be conducted to determine the stator faults. For the first test to check an open circuit in the winding, set a multimeter to test resistance. Connect the multimeter to the two ends of each wire, and examine the reading. Your stator could have an issue if it isn’t within manufacturer specifications.

The second test determines if there is a short between the ground and the stator windings. Connect one of the test lead to a clean frame ground on the generator and another to the stator lead specified in the owner’s manual. The stator winding has a ground fault if the meter doesn’t read overload or infinity.

The final test for a brushless stator is done to determine if a short exists between windings. After consulting the owner’s manual for which leads to use, place your test leads on the manufacturer’s specified leads in the stator. The multimeter should read overload or infinity. Any other outcome indicates a short between the stator’s windings.

For a brushed stator, begin by disconnecting the device from both the electrical panel and the automatic voltage regulator. Set a multimeter to test resistance and place one of the test leads on a frame ground and the other on the stator itself. The multimeter should read overload or infinity. If this test fails, your brushed stator might need to be replaced.

#4 The Circuit Breaker (CB) Has Issues

An electrical circuit breaker is a critical part of any generator and can possibly be the cause of no or reduced power from the generator, depending on which circuit breaker has the problem. If the main circuit breaker has tripped out, you will not receive any power output. If any of the outgoing load circuit breakers have tripped, you will receive partial output. In the case of trappings, you need to locate the reason and rectify it.

If you cannot find any tripped breaker but do not receive full or partial power, you need to inspect and test the corresponding circuit breaker.

Diagnosing CB issues varies with the type of breaker. Some CBs have colored indicators signaling their status, but this is not a standard with all circuit breakers. A breaker without an indicator will need to be checked by a multi-meter.

Disconnect the CB and put it in the “ON” position. Set a multimeter to test resistance and place the test leads on the wire connections on both sides of the CB. If the multimeter detects any resistance, the circuit breaker is functioning normally. The CB is likely damaged if the multimeter reads overload or infinity in the closed position. 

If you’ve found your CB has gone bad, the defective breaker will need to be replaced. A circuit breaker replacement can either be done at home or with professional help, depending on your skill and comfort level working with generators.

#5 The Generator is Overloaded.

While it may sound obvious, generators can only produce power up to their rated limits. One of the most common reasons for a generator not putting out its full power is the machine being overtaxed with too many power devices. As a result, either the main or individual breakers may trip out, or there may be an excessive voltage drop on connecting loads.

Before buying any new parts or hiring someone to repair your generator, check it is not overloaded.

Aside from a reduction in power output, there are other signs your generator might be overloading, such as:

  • Generator Keeps Tripping
  • Indications On The Generator Control Panel
  • A Drop In Power Output
  • The generator is overheating, and the fans are overly loud.
  • Weird Noises Coming Out From The Generator
  • A soot buildup is in the exhaust port of the generator.
  • The generator is emitting smoke or sparks from its vents.

If you believe your generator is overloaded, there are ways to fix the issue. Begin by turning the generator off and allowing it to cool down before proceeding with repairs. Once cooled, disconnect any devices connected to the generator.

No matter the size, every generator has a maximum wattage it can produce. This information can be found on the generator itself or in the owner’s manual. Once you know the maximum wattage of your generator, you’ll need to find the wattage used by all the electrical devices attached to it.

Some devices, such as refrigerators, use more power to start up than run. Keep the starting wattage of the devices in mind when totaling up their power use. If the totaled wattage exceeds the generator’s maximum capacity, you will need to keep some devices disconnected from your generator before turning it back on.

If the wattage information for items plugged into a generator is difficult to find, it can be tested by running the generator with only one appliance attached to it. Repeat the process by adding new items, one at a time, to see the generator’s limit.

Once you’ve sorted out your wattage issues, simply restart your generator and plug your devices back into it up to the generator’s limit. If the generator still is not putting out full power, this can be a sign it is still overloaded. It is also possible a mechanical issue exists and needs to be repaired.

We have covered the issue of Generator overload, its impact, reasons, and fixes in great depth in our article “How To Fix An Overloaded Generator?

#6 The Automatic Voltage Regulator Needs Replacement

An automatic voltage regulator, or AVR, is responsible for maintaining the voltage output of the generator at the desired levels.

Testing the AVR should be done after determining the generator is not running over its capacity, the stator is undamaged, and the circuit breaker is functioning normally. It is much more difficult to determine if the AVR is at fault if any of the previous fixes have not been tried.

If you review section 1 above, you will find AVR faulty, misadjusted, and problems in sensing and power circuits are the likely reason for the majority of the issues except for one receptacle failure or the alternator delivering 8 to 12 V.

Start testing the AVR by making sure it is not out of adjustment, and the power and sensing voltage to the AVR and related wiring is correct. Once the device is readjusted, attempt to use the generator again and see if the power output has increased.

If there is no output voltage at all, carry out the rotor excitation test by infusing a battery voltage into the rotor. If the rotor is still not producing any output, the rotor, diodes, or other output components like rotor brushes can also have the problem and needs to be checked. Else, the AVR has an issue and should be replaced.

Replacing the AVR is a simple process. As with any generator repair process, ensure the generator is off before beginning repairs. Start by removing the generator head and locating the faulty AVR. Detach any wires and screws from the current AVR, and replace the old AVR with the new one. A new generator AVR can be a simple fix to the generator issues.

#7 The Capacitor is Malfunctioning

The capacitor is another vital component of a generator; an issue with it could cause generator malfunctions. Capacitors serve two primary functions in a generator. Primarily, they assist in the buildup of the voltage due to the residual magnetism to the full terminal voltage during startup. Additionally, capacitors regulate the voltage in a generator.

First, check for visual signs of deterioration or damage, as detailed in our article on “Capacitor for Generator.” If there are no tell-tale visual signs, check its condition with a multimeter.

To check a capacitor, you need to disconnect it from the generator. But before that, it must be discharged. Discharging a capacitor involves releasing all of its stored energy by hooking it up to a resistive load like a power resistor or a simple light bulb for a few seconds. Alternatively, a screwdriver with an insulated handle can get the job done.

Following the discharge and disconnection of the capacitor, take a reading by a multimeter with the ability to test capacitance. The measurement should be within a tolerance of five microfarads, uF, of the rating printed on the capacitor. If the reading does not meet this threshold, the capacitor will likely need to be replaced to get the generator back up and running.

#8 The Alternator Was Idle for Too Long

The alternators of conventional generators use the residual magnetism of the rotor core to produce a voltage of 4 to 12 V at no load. The capacitor placed across the stator excitation windings helps in building up this small voltage to its final value. If a generator has not been used in some time, it can lose its all-important magnetism, which is so crucial to its functioning.

An alternator with a loss of residual magnetism will need to be field flashed, as it’s known in the industry. This process can be difficult, especially for anyone not comfortable working on generators. It is much better to take your generator to an electrical professional who can perform the process.

To avoid alternator issues, you should run your generator regularly. Similar to the concept of regularly running a car even when it is not in use, this can keep the alternator from losing its magnetism. Even if a generator is not needed, it can still be useful to let it run for some time to regain its charge. It can also save money on fixing an alternator down the road.

#9 Mechanical Issues are Hampering the Generator

If none of the previous solutions fix a generator issue, some minor mechanical issues may be hindering the generator from producing power at the required levels.

If the generator’s fuel supply system, including valves or fuel filters, is clogged, the issue can block fuel from circulating inside the generator. A generator with a lean fuel mixture will have a lower power output and rough, uneven running.

Other issues may include a non-responsive engine governor, leakage of air to the carburetor through the gaskets, clogged air filters resulting in less air for combustion, worn rotor shaft bearings, issues with the spark plug or the ignition system, inadequate compression, issues with the 12V voltage generator, etc.

While either of these problems will significantly affect the abilities of a generator, they can be repaired by talking to an electrical professional. These fixes are not too serious and are relatively low cost.

The Bottom Line

Troubleshooting a portable generator can be difficult and time-consuming, but these tips can ease the burden. Did these tips help you diagnose the problems with your generator? Have you tried other methods to repair a generator not putting out its full power? If so, discuss them in the comments.

Leave a Comment