No Output · Gauteng
Engine Running.
No Power Out.
If the generator is running and the building is still dark, the fault is electrical. We measure output at the alternator, breaker and changeover switch before any AVR or rewind work.
- Output voltage diagnosis
- AVR and breaker checks
- Alternator winding tests
- Onsite Gauteng repairs
The Fault
Running without voltage is an electrical diagnosis
When the engine is running at the right speed and the building still has no power, the fault is on the electrical side of the set. Owners often assume the generator is “broken” as a whole. In practice the diesel or petrol engine may be healthy, while the AVR, a tripped output breaker, lost residual magnetism or a winding fault is sitting between the alternator and your DB.
The first split is simple: is there voltage at the alternator terminals, and is that voltage reaching the changeover switch? A tripped breaker or a failed transfer contact can look like a dead generator while the alternator is producing normally. We measure both sides before opening the AVR or talking about rewinding.
If terminal voltage is missing or unstable, we test the automatic voltage regulator and the excitation circuit. Many no-output jobs in Sandton offices and Johannesburg warehouses are AVR failures — the engine note is fine, lights stay off. Unstable voltage that rises and falls with load is the same family of fault, not a fuel problem.
Where windings are open, burnt or have failed insulation, that is a different repair path. We only recommend rewinding after electrical tests show the AVR and breakers are not the cause. Guessing “it’s the alternator” is expensive when a regulator or breaker would have restored output.
Set running, no power?
Call or WhatsApp 082 057 4605 for output voltage diagnosis across Gauteng.
082 057 4605What You Might See
How no-output usually shows up
01
Engine runs, zero volts
Normal exhaust note, no voltage at the outlets or DB. AVR, excitation, residual magnetism or a main breaker that has opened.
02
Voltage too low to use
Lights dim, UPS units drop, motors will not start. Often AVR calibration, a failing regulator or a winding beginning to break down.
03
Voltage hunting
Readings swing as loads switch. Connected equipment suffers. This is treated as an AVR or excitation problem, not an engine speed issue, once RPM is confirmed stable.
04
Power on the set, none in the building
The generator panel shows voltage, the premises stay dark. Look at the output breaker, changeover switch and cable connections before the alternator.
What We Check
Where generator power is lost
Output breaker
Thermal or magnetic trips after a fault. Resetting without finding the load fault will trip it again.
AVR / voltage regulator
No excitation means no usable output even with a healthy engine and stator.
Excitation winding
Open or shorted excitation prevents the AVR from building voltage. Confirmed with resistance tests.
Stator and rotor
Insulation breakdown and burnt windings need electrical testing, then rewind or replacement — not a new AVR on a damaged machine.
Changeover / ATS
The set can be live while the building stays on a failed transfer contact. That is a control and switching job.
Output cables and lugs
Burnt lugs and loose glands create voltage drop or open circuits after vibration and heat.
How We Diagnose
Measure the path before replacing the AVR
- 01
Confirm engine speed
We check that RPM is stable. Low speed can collapse voltage and is an engine or governor issue, not an AVR first step.
- 02
Measure at the terminals
Voltage at the alternator, then after the breaker, then at the ATS. That sequence shows where output is lost.
- 03
Test AVR and windings
Regulator output, residual magnetism and winding insulation are tested only after the path to the load is understood.
- 04
Repair and load-check
After the repair we verify voltage under real load, not only at no-load idle.
Specialist Follow-On
AVR, switching or windings — not the same repair
No output is the symptom AVR repairs exist for. If tests show the regulator or excitation circuit has failed, we repair or match a replacement to the alternator — a generic AVR that is not calibrated will recreate low or high voltage.
If insulation tests fail, the conversation moves to generator rewinding. Those two pages are the specialist follow-ons from this diagnosis, not interchangeable jobs.
AVR repair
Restore excitation and stable voltage
Breaker and ATS
When the set is live but the building is not
Rewinding
When windings have actually failed
Load check
Prove output at light and working load
Common Questions
No power from a running generator
Why does my generator run but produce no power?
The engine can be healthy while the AVR has failed, an output breaker has tripped, residual magnetism is lost, or windings are open. We measure voltage at the alternator before recommending any of those repairs.
Is no power always the AVR?
No. It is a common cause when the engine note is normal, but breakers, transfer switches and winding faults produce the same dark building. Replacing the AVR first without tests wastes the part.
Can a tripped breaker look like a dead generator?
Yes. If the engine is running and the panel shows voltage, the next check is the output breaker and changeover switch. Resetting a breaker without finding the overload or short will not hold.
Will this damage appliances?
Unstable or high voltage can. If lights are surging or equipment is tripping, stop using the set and have output measured. Running into a failed AVR is harder on connected loads than on the engine.
Still unsure what the fault is? Call or WhatsApp 082 057 4605 for onsite diagnosis.
Service Areas
No-output callouts across Gauteng
We diagnose generators that run without power in Johannesburg, Pretoria, Sandton, Centurion, Midrand, Fourways and surrounding areas.
Book a Diagnosis
Running, but nothing on the board?
Tell us whether the engine sounds normal and whether any voltage shows on the generator panel. That separates AVR work from transfer-switch work.
- Call
- 082 057 4605
- Message us on WhatsApp