If you live in an RV or an off-grid homestead, a generator is your main power source. Unless you rely on solar energy, and even then, it may not be a reliable source come winter. As such, your generator must always be in top shape to serve your energy needs.
So what do you do when your generator is running, but no power is produced?
Here are the reasons why your generator is running without producing power and how to fix it;
First and foremost, if you’re not getting power to your appliances after you’ve turned on the AC power switch from your generator, you should check to verify that you don’t have a tripped breaker.
There are two types of breakers that you might encounter:
- Circuit Breaker (fuses)
- GFCI Breaker
If your generator engine is running but produces no or low output, the circuit breaker is the first thing you should check. The breaker is a safety feature designed to automatically switch off if a surge of electricity or overload is detected.
A surge can be caused by using a device that draws more power than the breaker is rated for, using multiple ‘heavy load’ devices simultaneously, or if a short occurs within the circuit.
Some breakers will have colored indicators to show if they have been tripped, but some will not give any indication. Cycle the breaker off and on and try the outlet again.
If the outlet is still not working, confirm that the breaker is set to the on position and use a multimeter to measure the resistance on the lead wire connections inside the electrical panel. If any resistance is read, then the breaker is good. On the other hand, if the meter reads ‘OL’ (overload) or Infinity, the breaker is bad and should be replaced.
GFCI breakers are designed to trip when they sense there isn’t enough power to complete the circuit on the circuit’s designated route. They are programmed to sense a certain amount of power. If that power deviates from the norm, it trips and saves you from being shocked.
Another common way to trip circuit breakers is to use the wrong gauge of wire for what you’re trying to power or plug multiple cords together.
Remember that it might just be a particular item tripping your breaker, and it might not necessarily have anything to do with your generator. So test other items out and even items of comparable wattage to see if the affected breaker still trips.
If it is a true emergency and you cannot get a generator to work, and you are certain that the breaker is at fault, you can technically bypass your breaker altogether.
With the generator running, ensure the AC power is turned on and the breaker is not tripped. Use a multimeter to measure the AC voltage by placing the black lead in the smaller slot on the right (of a 120v outlet) and the red lead in the longer slot on the left. You might have a bad outlet if you are not getting any reading. Replace if necessary.
Loss of Residual Magnetism in the Alternator
Once you’ve verified that your breakers are not the problem, the next thing to do is see if you’ve got a loss of residual magnetism in your alternator.
Like those in your generator’s alternator, Electromagnets need a bit of residual magnetism to be “primed” to get the electrical generation process going.
There are a few things that lead to the loss of residual magnetism;
- Lack of use can cause a generator to lose residual magnetism. Over time the reserve of magnetism is slowly depleted. Until it eventually runs out.
- You keep things plugged into the generator when you turn it off. So if the generator is powering a load when turned off, its magnetism will be sucked into the load.
- You leave the generator running for too long without plugging it into anything. This can cause the electromagnetic field within the generator to shut down.
This is the last thing you can easily check visually without learning to use a multimeter to check resistance and voltages. When you remove the cover to your generator’s alternator.
Remove the bolts holding the alternator cover in place. The black brushes stick out of the gray plastic housing and are spring-loaded (you can push them into the gray housing, and they’ll pop back out). If they are deformed or damaged, you’ll need to replace them.
Usually, right above the bearing, you will see two spade connectors that connect to the brushes made from carbon material that makes contact with the rotor.
They are held in place by a screw. With the generator off, take a picture of how everything looks. And the orientation of the wires and remove the spade connectors. Then, remove the screw.
Pull out the brush assembly and check to see if they look damaged, broken, or are sticking. The brushes are small rectangular carbon pieces that can be pushed into the assembly but want to pop back out.
Check the assembly itself for any burn marks or anything that doesn’t look right. Your brushes are likely fine, but if they aren’t, go ahead and replace them.
The alternator uses residual magnetism from the windings to charge the capacitor. If the generator has not been used for an extended period, the magnetism can be lost, and the capacitor will not be charged.
When this occurs, the capacitor must be ‘field flashed’ to restore its charge so the rotor can once again be excited. To charge the capacitor, a special charging harness must be constructed using a short length of 12-gauge wire with a standard 120v plug on one end.
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The opposite end should have a few female blade connectors attached to the capacitor’s terminals. Finally, a single-pole momentary switch is added to the live or positive side of the wiring harness.
Connect the harness to the capacitor’s terminals and plug in the plug end to a 120v outlet. The momentary switch should be depressed for not more than one second.
This will restore the charge of the capacitor. It can then be reinstalled in the generator. Once the capacitor is charged, care must ensure no shorts are created between the terminals while reinstalling.
Again, if there is any doubt or confusion about this process, take the generator to a professional to perform this repair.
Damaged Automatic Voltage Regulator (AVR)
The AVR is a circuit that regulates and balances the amount of voltage being output from the generator. All AVRs will have an adjustment screw that allows for fine-tuning the voltage output. Diagnosing a faulty AVR is done by process of elimination; Start by testing the generator’s main circuit breaker.
Suppose the breaker tests are good for continuity, test the wiring within the electrical panel and from the breaker to the stator. If the wiring tests good, try adjusting the AVR to ensure it is not out of adjustment.
If there is no change in output, check the rotor brushes to ensure they are in good condition and are making contact with the rotor. If everything tests good up until this point, test the stator itself. If the stator is producing power, the AVR is faulty and needs to be replaced.
Use a multimer to test your AVR. First, take the leads off from the brush assembly. Then unscrew and remove the entire AVR.
Start up the generator with the end plate still off. While it’s running, take readings:
- From the brushes.
- From each pair of windings. The four small terminals are lined up on one side of the alternator.
- From the two positive winding terminals.
The readings across the brushes should be somewhere between 5 and 10 volts. Across the windings, they should be more like 3-5. And there should be no voltage across the positive winding terminals. If these voltage readings are normal, the AVR is what’s messing up your generator. You’ll need a fresh one.
If you’re getting readings outside those ranges, there’s a problem with your alternator’s rotors or windings.
The capacitor has two functions; it induces a voltage into the rotor and regulates the voltage. A bad capacity will result in a low voltage reading from the generator as the power generated will be from the residual magnetism of the rotor (usually about 2-5V).
To test a capacitor, a multimeter that can test capacitance is required. The capacitor must first be removed from the generator and discharged. Be careful when removing the wire leads that a short is not created across the capacitor’s terminals.
To discharge, use a screwdriver with an insulated handle to cross the terminals on the capacitor (this will result in a loud pop and a spark).
Once discharged, take a reading from the capacitor. The measured capacitance should be +/-5uf of the specified rating printed on the side of the capacitor. If not, the capacitor should be replaced.
Many home generators use capacitors instead of AVRs to control their voltage. Unfortunately, these can also cut off your machine’s output when they fail. If you have a brushless generator, you should test the capacitor to see if this is what’s blocking your power.
You’ll find it in roughly the same spot where an AVR would be. Use extreme caution when working with capacitors. Don’t let your finger connect the two terminals. This could result in a severe shock.
You may see obvious damage signs such as melted metal or scorch marks. If not, leave the cover off and turn on your generator. While the engine is on, touch the probes of your multimeter to the two ends of the capacitor.
Faulty Generator Stator
There are two types of stators used in generators; brushed and brushless. The stator is typically made up of three windings; two power windings and one winding that is used to either excite the rotor on a brushed stator or charge the capacitor on a brushless stator. The magnetically charged rotor rotates inside the fixed stator windings, producing electricity.
How To test a brushless stator,
The wires from the stator to the electrical panel will need to be removed first. You will also need some information from the manufacturer; the function of each stator wire and the normal resistance reading for each of the coils within the stator. Once this information is found, you can begin testing.
The first test will determine if an open circuit within the winding indicates a damaged or broken winding. Using a multimeter set to test resistance, connect the multimeter to each end of the wire coil using the leads. The meter should give a resistance measurement within the manufacturer’s specifications.
Reading outside of this spec will indicate a bad winding. Perform this test on both power windings. The next test will check for a short between the windings and ground. The manufacturer will specify which stator lead to use for this test. Set the multimeter to test resistance.
One test lead will be connected to the stator lead specified by the manufacturer, and the other will be connected to a clean frame ground on the generator.
The meter should read “OL” (overload) or Infinity. If the resistance measurement is detected, the stator likely has a short-to-ground condition.
The final test for a brushless stator is to test for a short between windings. Again, the manufacturer will need to specify which leads to use for this test. Set your multimeter to test resistance.
The test leads will be connected to two of the stator leads specified by the manufacturer. The two leads will be one lead from each of the power windings.
The meter should read “OL” (overload) or Infinity. If the resistance measurement is detected, that would indicate a short between the windings in the stator. This test is meant for brushless generators.
How To test a brushed stator:
Isolate the stator by removing the connections to the AVR (automatic voltage regulator) and the wires running from the stator to the electrical panel. Set your multimeter to test resistance. One of the test leads should be connected to a clean frame ground, and the other used to test each of the leads from the stator.
Each lead should read “OL” (overload) or Infinity. If any of the leads give a resistance measurement, that would indicate a short to ground and a bad Stator.
How to restore residual magnetism in a Generator
Below are two main methods you can use to remagnetize a generator;
12 Volt Generator Battery Method
Locate the voltage regulator for your generator. Unplug the two wires that connect to the generator brushes. Usually, one is red, and the other is black or white. Connect the black or white to the generator ground battery terminal.
Plug in a light, turn on the generator breaker or switch, and start the motor. Connect the battery +12 volts red cable to the red wire on the terminals you removed for three seconds.
Remove your wires and replace the plug. The generator should now be producing power again. Ensure you unplug the brush wires from the automatic voltage regulator, or you will damage the regulator.
Safety Tip: Do not touch the voltage regulator or other wires as dangerous voltages may be present that can cause electric shock.
Electric Drill Method
Plug an electric drill into the generator receptacle. If the drill is reversible, move the direction switch to the forward position. Then, start the generator while depressing the trigger on the drill.
Spin the drill chuck in the reverse direction. This will excite the field, and the generator will now produce electricity. If turning the chuck in one direction does not work, try spinning the chuck in the other direction, as you may have the reverse switch positioned backward.
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Use caution not to get your hand or other materials caught in the chuck. As soon as the field is exited, the generator will produce power, and the drill will turn on.
Note: If these methods do not help you restore generator output power, replace the Automatic Voltage Regulator as it may be damaged.