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ProService Generator Repairs

Alternator repairs

Leroy-Somer Generator Alternator Repairs & Servicing

Leroy-Somer makes the alternator on many diesel generator sets. When your set runs but gives no voltage, low voltage or unstable voltage, or a winding has failed, we diagnose and repair the alternator on site across Gauteng and quote before any work.

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Blue generator alternator inside a canopy, with the service date and next-service hours written on the air filter

What a Leroy-Somer visit covers

We start with your complaint, because no voltage, low voltage and unstable voltage are three different faults. We check the excitation, the AVR, the breaker and the wiring before we condemn the windings. For the wider picture, see generator alternator repairs, and if your set runs while the building stays dark, generator not producing power.

When the electrical tests point to the machine itself, we assess the windings and the insulation, and we note any bearing noise or mechanical wear we find. We recommend a rewind only when it is the right repair, through our generator rewinding service.

Regulator faults, from no output to high or unstable voltage, are covered in more depth under AVR repairs, generator low voltage and unstable voltage. If your diesel set will not start at all, that is an engine and control fault, handled through diesel generator repairs.

ProService Generator Repairs services and repairs Leroy-Somer alternators. We match parts to the alternator model on its plate and confirm availability in the quote.

Symptoms

How a Leroy-Somer output fault presents

Your symptom decides our first test. Each of these looks like a generator that is not doing its job, and each has a different cause.

  • Engine runs, no output at all

    The set starts and holds speed, and nothing reaches the board. We test the breaker, the excitation circuit, the AVR and the main windings, because a healthy engine says nothing about the alternator end.

  • Voltage present but low

    Output appears but sits below where it should. The AVR, the excitation supply, engine speed or a winding can cause it, and we measure it on the running set.

  • Voltage will not settle

    Readings wander or lights flicker. A changing load, unsteady engine speed and a regulator that is not controlling properly all look alike, so we settle the engine side first.

  • Output collapses under load

    Voltage looks fine off load and falls away when the load comes on. That test tells us whether the excitation or windings are limited, or the regulator simply needs setting.

  • Voltage high or rising

    We treat over-voltage as urgent, because it damages connected equipment. Switch off sensitive appliances and call us; we take the set off load before investigating further.

  • Noise or heat at the alternator end

    Bearing noise, a burnt-insulation smell, heat or discolouration point to mechanical or insulation damage, and we record them even when your original complaint was electrical.

The sequence

What we test, and in what order

We run the quick, reversible checks before we dismantle anything. A rewind is where the evidence leads, never where we start.

  • 01

    Confirm the engine side first

    We confirm engine speed and stability before judging the output, because an engine off its governed speed causes voltage and frequency symptoms that look like alternator faults.

  • 02

    Check breakers and connections

    An open breaker, a loose terminal or a damaged cable can leave the board dark with nothing wrong inside the machine, so we check them before opening the alternator.

  • 03

    Measure at the terminals

    We take readings on the running set, so the fault is defined by measurement as well as by the symptom you describe.

  • 04

    Test the excitation and AVR

    We test the regulator and its supply as one circuit. Swapping an AVR without finding why there is no output can leave the real fault in place.

  • 05

    Assess windings and insulation

    When the electrical tests point at the machine itself, we examine winding condition and insulation. This step separates a repairable fault from a rewind.

  • 06

    Report, then quote

    We explain the finding and give you a written quote before we change any part, including parts availability for your alternator.

Why the alternator is a separate diagnosis

On most standby sets, different manufacturers build the engine and the alternator. Leroy-Somer makes the alternator, and the engine beside it may be a Perkins, Cummins, Deutz or another make entirely. That matters when you book, because an engine that will not start and an engine that runs without producing power need different tests and equipment.

It matters for parts too. An AVR or a winding repair follows the model on the alternator plate, not the engine badge on the canopy. That is why we ask for a photo of the alternator plate, the kVA and the alternator model before we visit.

If the engine itself is the problem, see diesel generator repairs. If the set never turns over, start with generator not starting. If it runs and the board stays dead, generator not producing power is the closer match.

Leroy-Somer alternator questions

Do you repair Leroy-Somer generator alternators?

Yes. We inspect and repair Leroy-Somer alternators fitted to generator sets across Gauteng, whichever engine drives them.

Why does the engine run and the Leroy-Somer alternator make no voltage?

With the engine running, no output usually comes from the breaker, the AVR, the excitation circuit or the alternator windings. A healthy engine tells us nothing about the alternator, so we test it separately.

Can low or unstable voltage be an AVR fault?

Yes. Low, high or unstable voltage can come from the AVR, the excitation circuit, engine speed, wiring or the windings. We confirm the cause before we replace any part.

Do you rewind Leroy-Somer alternators?

Yes, when a rewind is the right repair. We assess winding and insulation faults first and handle the rewind through our generator rewinding service. Many electrical faults are fixed without one.

Is Leroy-Somer a diesel engine brand?

No. Leroy-Somer makes alternators, the electrical end of a generator set. The engine beside it may be a Perkins, Cummins, Deutz or another make, and we repair those through our diesel generator repairs service.

What should I send before the visit?

A photo of the alternator plate, the generator kVA and a description of the voltage fault. Tell us whether the engine starts and whether any voltage appears.

Where to go next

Voltage faults, rewinding and the engine side