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BEFORE YOU START
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DISCLAIMER:
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.
Our pictorials are of informative nature and do illustrate works carried out by ourselves at our own premises for our own use and satisfaction.
Readers who envisage to carry out similar works inspired by the below method shall do this at their own risks and liability.
How to access a small diesel generator electrical components
In most small diesel generators, electrical components are located between the alternator and the exhaust mufflers.
To access them, simply remove the right side panel and the exhaust mufflers.
To access them, simply remove the right side panel and the exhaust mufflers.
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There are two different models of AVRs however, one shaped like half-moon and found between the alternator and the exhaust like for other devices, and another rectangular AVR that is located inside the back panel of the generator canopy.
If your generator is equipped with the rectangular AVR, you also need to dismantle the back panel.
If your generator is equipped with the rectangular AVR, you also need to dismantle the back panel.
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Diagnostic of a small diesel generator that does not generate power
You might need to check the electrical diagram of your generator, click on the below link if this is the case, or else proceed with our tutorial.
If your generator started providing erratic voltage (for example 270V or more), or if the voltage is fluctuating, or if it stopped completely delivery power while the engine is running well, then you might need to diagnose the below components.
Symptoms of a faulty generator AVR:
- High voltage
- Low voltage
- Fluctuating voltage
- No AC output
- Engine doesn't turn off electrically anymore, need to turn it off mechanically with the red lever *
STEP 1: checking the main electrical bar that connects all windings
Start by visually inspecting the plastic connector to which all windings of the alternator are connected, and from where two wires are taken up to the socket outlets.
In this case, it was found broken, with the lower connector loose and partially melted.
The repair consists of :
Start by visually inspecting the plastic connector to which all windings of the alternator are connected, and from where two wires are taken up to the socket outlets.
In this case, it was found broken, with the lower connector loose and partially melted.
The repair consists of :
- disconnecting all wires
- testing with an ohmmeter the resistance of the windings and confirming it is not open, rather low and that reading between wires 1 and 2 is identical to the one between wires 3 and 4.
- replacing the broken connector with a new one and solidly fixing all wires and connectors
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STEP 2: checking the excitation carbon brushes:
Unscrew the bolt that holds the carbon brushes holder and take it out to inspect the bruches.
Make sure both are of equal length and that they are at least 6mm long or else, replace them and proceed to step 3.
Unscrew the bolt that holds the carbon brushes holder and take it out to inspect the bruches.
Make sure both are of equal length and that they are at least 6mm long or else, replace them and proceed to step 3.
AVR replacement on a small diesel generator
STEP 3: replacing the AVR:
You cannot test the AVR, it has to be replaced systematically in any of the below troubles:
Do not worry about mixing the wires, this is not possible since each and every connector is different from the other.
You cannot test the AVR, it has to be replaced systematically in any of the below troubles:
- fluctuating voltage
- voltage falls under load
- high voltage
- low voltage
Do not worry about mixing the wires, this is not possible since each and every connector is different from the other.
Testing the DC output of the small diesel generator
STEP 4: DC power bridge testing:
Before reassembling the generator, it is worth checking the power bridge which delivers 12VDC output for charging a battery.
Disconnect the diodes bridge wires and test the bridge with the ohmmeter on the diode testing position.
Before reassembling the generator, it is worth checking the power bridge which delivers 12VDC output for charging a battery.
Disconnect the diodes bridge wires and test the bridge with the ohmmeter on the diode testing position.
Final step: adjusting the AVR output
Reassemble the generator, except the back panel, start it and test its output voltage.
In most cases, it will deliver the required 220 or 230V but in some cases, you might notice a higher voltage and you will need to adjust its output.
If the voltage is not between 220 and 230V, and while the generator runs, find the small screw of the potentiometer which is factory blocked with a black compound, and force it to rotate it either way while reading the output voltage.
Adjust it to the required output with the generator still having no load, then load the generator with a heater or hot air gun and check that the voltage remains the same.
Reassemble everything as you will be done with your diagnostic and repair.
In most cases, it will deliver the required 220 or 230V but in some cases, you might notice a higher voltage and you will need to adjust its output.
If the voltage is not between 220 and 230V, and while the generator runs, find the small screw of the potentiometer which is factory blocked with a black compound, and force it to rotate it either way while reading the output voltage.
Adjust it to the required output with the generator still having no load, then load the generator with a heater or hot air gun and check that the voltage remains the same.
Reassemble everything as you will be done with your diagnostic and repair.
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