Load faults
Generator Trips or Shuts Down Under Load
The generator is fine until something is connected, and then it trips, slows, or shuts down. Unloaded running has not proved the set. Possible causes include overload, a set that is small for the starting current, fuel that cannot keep up, frequency or voltage that collapses, a breaker, the alternator, overheating, or a controller protection that only appears under load.
- Unloaded is not a pass
- Speed, voltage and heat
- Load testing when capacity is the question
- Onsite across Gauteng
When the building connects
Why does a generator run fine until load is applied?
Because the fault needs current, fuel flow, or heat that an empty run never asks for. A motor, a lift, a cold room or the whole board can demand more at the moment of connection than the set can start and hold.
The visit records what was connected when it tripped, whether the engine note fell, whether voltage sagged, and whether a breaker opened or the controller shut the engine down. Those are different endings to the same complaint.
If the question is whether the generator is large enough, or whether it can still make its rated output, a load bank test is the controlled way to see that. The size guide explains why nameplate kVA is not the whole answer.
What changes under load
Overload, fuel, voltage, breakers and heat
Generator overload
The connected load, especially motors starting together, can be above what the set can carry. That is a sizing and sequencing question as well as a repair.
Fuel and engine power problems
A restriction that is invisible off load can starve the engine once it is asked to work. Filters and delivery are checked before the governor is adjusted.
Voltage and frequency drop under load
If speed falls, frequency falls with it, and voltage often follows. Those readings are taken while the load is applied, not only at idle.
Breaker trips
A breaker opening is not the same as the engine shutting down. The trip, the current and the cable are part of that result.
Generator overheating under load
Temperature protection may only appear after a run with load. Coolant and airflow are checked against that pattern, on the overheating page when heat is the alarm.
Load bank testing
Used when a building start is unsafe or unclear, and the set needs a known load instead.
Generator size versus connected load
The plate kVA is the start of the comparison. Starting current, three-phase balance and later equipment decide whether the plate is enough.
Related Pages
Load, size, speed and heat
Google reviews of ProService Generator Repairs
Google Review
Our Hyundai petrol unit couldn't hold a steady load when the fridge kicked in. They adjusted the voltage regulator and throttle linkage, completely stabilizing the output.
Google Review
We suspected our aging plant was losing capacity, so they performed a load bank test. The detailed graphical report proved the alternator was struggling, allowing us to upgrade proactively.
Common Questions
Questions about generators that trip under load
Why does my generator trip only when I connect the load?
The unloaded run is not asking for the current, fuel or cooling that the load needs. The failure shows up when that demand arrives.
Does a trip mean the generator is too small?
It might. It can also be fuel, speed, a breaker, voltage or heat. Size is considered after those are separated.
The engine note drops when the lights come on. What is that?
Possible causes include overload and a fuel or governor limit. Frequency is read while it happens rather than adjusted by ear.
A breaker opens but the engine keeps running. Is that an engine fault?
Not necessarily. An electrical trip with the engine still running is a different fault from a shutdown that stops the engine.
Can one large motor cause the trip?
Yes. Starting current can be several times the running current. What starts at the same moment matters.
Will a load bank test show this?
It shows whether the set can carry a defined load. It is booked when that is the question, not as a substitute for a breaker or fuel fault that is already obvious.
It also gets hot and then stops. Is that the same page?
Heat after a loaded run is the overheating checks. Mention both symptoms so the visit watches temperature as well as the trip.
What should I list when I book?
What was switched on, whether the engine stopped or a breaker opened, and the kVA on the plate.
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
Say what was connected when it tripped
The kVA, the fuel, and whether the engine stopped or a breaker opened are the three useful facts.
- Call
- 082 057 4605
- Message us on WhatsApp