Alternator repairs
Generator Alternator Repairs & Testing
We test and repair generator alternators when the engine runs but the electrical output is wrong: no power, low voltage or voltage that will not hold steady. Many of these faults sit in the AVR, the excitation, a diode or a connection, so we test those before we talk about rewinding. Rewinding is a separate job for windings that have actually failed.
Callout fee waived when you accept our written quote. 1-year workmanship guarantee. See prices
- Output tested before any rewind
- AVR tested separately from the alternator
- Stamford alternators repaired
- Onsite across Gauteng
The output end
How do you know if a generator alternator is faulty?
The clearest clue is an engine that runs normally while the electrical output 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, so we check the breaker, the wiring, the excitation path and the AVR first.
The cause can be a failed AVR, lost excitation, a diode or capacitor fault where your alternator uses them, loose or burnt connections, damaged insulation, or a stator or rotor winding fault. Each one shows up differently on our meters.
We recommend a rewind only when the winding tests show the copper or the insulation has failed. As a guide, alternator rewinding costs from R6,000 to R18,000 or more, depending on the machine, and you get a written quote before we start.
What our meters separate
No power, low voltage, and AVR versus the alternator
Generator producing no power
The engine note is steady and there is no usable voltage. We check the breaker and the excitation before we condemn the windings.
Low or unstable voltage
A steady low reading and a reading that hunts are different faults. Both can come from the AVR, the engine speed or the alternator, and we measure to separate them.
AVR versus alternator faults
The regulator controls the alternator, and the alternator makes the power. Replacing one when the other has failed does not fix the output.
Generator winding problems
We run insulation and winding tests once we have ruled out the excitation and the AVR. A burnt smell is a clue, not a reason to rewind.
When is rewinding required?
When our tests show the windings have failed and a rewind is the right repair. Low voltage on its own never decides that.
Alternator testing
We measure output voltage, excitation and the connections with the engine running and stable. Live terminals are our job, never a customer check.
Related Pages
Output, voltage and rewinding
- Generator Rewinding Winding repair when the tests call for it
- AVR Repairs The regulator, not the windings
- Not Producing Power Engine runs, no usable output
- Low Voltage Voltage is present but low
- Unstable Voltage Voltage moves or flickers
- Stamford Alternators Self-excited and PMG machines, AVRs and diodes
- Leroy-Somer Alternators Testing and repairs for Leroy-Somer machines
Common Questions
Questions about generator alternator repairs
Do you repair generator alternators?
Yes. We diagnose output faults on site and repair the alternator when our tests show it is the part that failed.
Is an alternator repair the same as a rewind?
No. Many output faults are the AVR, the excitation, a diode, a capacitor or a connection. Rewinding is only for failed windings.
The engine runs and there is no power. Is that the alternator?
It might be. The breaker, the AVR and the wiring can cause the same thing, so we test those before the windings.
Can low voltage be an alternator fault?
Yes, but it can also be the engine speed, the load or the AVR. We take readings before we name a part.
Do you work on Stamford alternators?
Yes. ProService Generator Repairs services and repairs Stamford alternators. Stamford is one of the most common alternator makes on diesel standby sets, and we test and repair them on site.
Do you work on Leroy-Somer alternators?
Yes. Leroy-Somer is a common alternator make on diesel sets, and we test and repair them.
Should I adjust the AVR myself?
No. Turning a potentiometer on a live regulator can push the voltage the wrong way. We make that adjustment against a meter as part of the diagnosis.
Do you test the alternator after the repair?
Yes. We check the voltage with the engine running, and we book a load test when you need to know the set can carry its full rated load.
Still unsure what the fault is? Call or WhatsApp 082 057 4605 for onsite diagnosis.
Service Areas
Onsite visits across Gauteng
We come to your generator anywhere in Gauteng, 24/7. Choose your region for local suburbs, call-out details and the faults we see most there.
What to send before we attend
These details help us plan the visit and bring the right parts. Send what you can on WhatsApp; if you can’t find the model number, we still book the visit.
- 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
Tell us 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
What happens next
- We reply with questions about the generator, or to book a visit.
- A technician comes to you. For a breakdown we arrive within 1 hour.
- The fault is diagnosed on site and you get a written quote. No work starts until you accept it.
Charlie, lead technician: Degree in Mechanical Engineering, Degree in Electrical Engineering, Diesel Plant Fitter. Generator specialists since 2000.