Low voltage
Generator Producing Low Voltage
Voltage is there, and it is below what the set and the building should see. That is different from no power at all, and different from voltage that keeps moving. Possible causes include the AVR, excitation, the alternator, engine speed and frequency, overload, loose or burnt connections, a winding fault, or a sensing fault in the control circuit.
- A number, not a guess
- AVR separated from the alternator
- No home AVR adjustment
- Onsite across Gauteng
A low but real voltage
Why is my generator voltage too low?
Because something in the output path is not holding the voltage the plate describes. The meter comes before the part name. A dim-light complaint can be low voltage, low frequency, or a bad connection on one phase. Those are not repaired the same way.
Engine speed matters. If the set is not at the speed that produces the expected frequency, voltage often sits low with it. Chasing the AVR while the engine is slow treats the result and misses the cause.
Customers should not turn AVR potentiometers to “bring the voltage up”. That can push voltage too high once the real fault is removed, and it is done on a live regulator. The adjustment, if one is needed, is part of the measured repair.
What is measured
AVR, alternator, speed and connections
AVR faults
The regulator may be unable to drive excitation hard enough. It is tested, not turned up to hide a winding or speed fault.
Alternator and excitation problems
Lost excitation, a diode or capacitor fault, or a winding that can no longer support voltage. The alternator page is the hardware path.
Engine speed and frequency
Low Hz and low voltage together often start with speed. Frequency is read before the regulator is blamed.
Voltage drops under load
Acceptable off load and low once the building connects can be overload, fuel, or an alternator that cannot hold current.
Generator wiring and connections
A loose or burnt joint can drop voltage on one phase. That is found with the supply made safe to inspect.
How low voltage is diagnosed
Voltage and frequency are recorded off load and, where it is safe, on load. The stable low reading is kept separate from a reading that hunts.
Related Pages
Regulators, alternators and related voltage faults
Google reviews of ProService Generator Repairs
Google Review
Our Red Rhino was dropping voltage and damaging appliances. They immediately identified the faulty AVR, swapped it out, and load-tested the machine to confirm stable output.
Google Review
When our main plant dropped output voltage, they arrived with advanced diagnostics and identified a burnt stator that our previous contractor missed. They execute permanent, robust repairs every time.
Common Questions
Questions about low generator voltage
What counts as low generator voltage?
Output that is present but below the voltage the set should deliver for that supply. The meter decides it, not a dim-light guess alone.
Is low voltage the same as no power?
No. No usable output is a different fault. Low voltage means a reading exists and it is too low.
Is low voltage always the AVR?
No. Possible causes include speed, load, connections, excitation and the windings. The AVR is one of them.
Can I turn the AVR screw to raise the voltage?
No. That adjustment is made during the diagnosis, against a meter, not as a home fix.
The voltage is fine with nothing on and low when we connect. Why?
The set is not holding voltage under load. Overload, fuel, frequency and the alternator are then in the test.
Can one loose connection cause low voltage?
Yes, often on one phase. The joint is found and remade. It is not left as an AVR adjustment.
Do you repair the alternator if the voltage is low?
Only when the tests show the alternator is the failed part. Many low-voltage jobs stop at the AVR, the speed or a connection.
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
Send the voltage you measured
If you have a number, send it, and say whether it was off load or with equipment connected. Do not adjust the AVR first.
- Call
- 082 057 4605
- Message us on WhatsApp