Alternator repairs
Generator Alternator Repairs & Testing
This page is for the electrical end of the generator: the alternator that should produce voltage once the engine is running. Rewinding is a separate job, used only when the windings themselves have failed. Leroy-Somer machines have their own page.
- Output tested before a rewind
- AVR separated from the alternator
- Leroy-Somer has its own page
- Onsite across Gauteng
The output end
How do you know if a generator alternator is faulty?
The useful clue is an engine that runs while the electrical result is wrong: no power, voltage that is too low, or voltage that will not stay still. That still does not prove the windings have failed. The breaker, the wiring, the excitation path and the AVR are checked first.
Possible causes include a failed AVR, lost excitation, a diode or capacitor fault where that alternator uses them, loose or burnt connections, damaged insulation, or a stator or rotor winding fault. Each of those shows up differently on a meter.
A rewind is recommended only when the winding tests say the copper or the insulation is the fault. That work sits on the generator rewinding page. This page is the diagnosis and the repairs that come before that decision.
What the meter is separating
No power, low voltage, and AVR versus the alternator
Generator producing no power
The engine note is steady and there is no usable voltage. The breaker and excitation are checked before the windings are condemned.
Low or unstable voltage
A low but steady reading and a reading that hunts are different faults. Both can sit in the AVR, the speed, or the alternator.
AVR versus alternator faults
The regulator is the control. The alternator is the machine it controls. Replacing one because the other failed does not correct the output.
Generator winding problems
Insulation and winding tests follow when excitation and the AVR have been ruled out. A visual burnt smell is a clue, not a rewind order.
When is rewinding required?
When the tests show the windings are the failed part, and a rewind is the repair. That decision is not made from low voltage alone.
Alternator testing
Output voltage, excitation and the connections are measured with the engine running and stable. Live terminals are not a customer check.
Related Pages
Output, voltage and rewinding
Google reviews of ProService Generator Repairs
Google Review
The engine ran perfectly but delivered zero electricity. They accessed the alternator, discovered a blown excitation capacitor, and soldered a high-grade replacement to restore power output.
Google Review
Solid, dependable servicing for Trade Professional generators. They replaced a worn stator and had our backup power restored right before a major power cut hit the area.
Common Questions
Questions about generator alternator repairs
Do you repair generator alternators?
Yes. Output faults are diagnosed on site, and the alternator is repaired when the tests show that is the failed part.
Is an alternator repair the same as a rewind?
No. Many output faults are the AVR, excitation, a diode, a capacitor or a connection. Rewinding is only the winding repair.
The engine runs and there is no power. Is that the alternator?
It might be. Possible causes also include the breaker, the AVR and the wiring. Those are tested before the windings.
Can low voltage be an alternator fault?
Yes, and it can also be speed, load or the AVR. The reading is taken before a part is named.
Do you work on Leroy-Somer alternators?
Yes. Leroy-Somer has its own page because it is a common alternator on diesel sets, not a diesel engine brand.
Should I adjust the AVR myself?
No. Turning a potentiometer on a live regulator can push the voltage the wrong way. That adjustment is part of the diagnosis, not a home step.
Do you test the alternator after the repair?
Yes. Voltage is checked with the engine running. A load test is booked when the question is capacity, not only whether voltage returned.
Still unsure what the fault is? Call or WhatsApp 082 057 4605 for onsite diagnosis.
Service Areas
Onsite visits across Gauteng
Technicians travel to the generator. These are the main Gauteng areas. Suburb pages sit under each region.
What to send before we attend
ProService Generator Repairs confirms an onsite visit from these details. Send what you have. A missing model number does not stop the booking.
- Location
- The suburb or site, so the visit can be booked in the right area.
- Make and model
- The generator brand and model, if they are known.
- kVA
- The size printed on the data plate.
- Fuel type
- Diesel, petrol, LPG, natural gas, or dual-fuel.
- Controller model
- The module name on the panel, when it is visible.
- Fault or alarm
- What the set does, and any text on the screen.
- Photos
- The generator, the data plate, and the controller or alarm. Send these on WhatsApp.
Book a Visit
Book an alternator diagnosis
Say whether the engine runs, and whether the voltage is missing, low, or moving. A photo of the alternator nameplate helps.
- Call
- 082 057 4605
- Message us on WhatsApp