Automatic start
Generator Not Starting Automatically
If your standby generator does not start when the mains fails, the fault is usually in the automatic start path: the ATS signal, the controller mode, an alarm or the battery. A set that will not start even from its manual button has a general no-start fault. We test the whole mains-fail sequence and prove it works before we leave.
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- Full mains-fail sequence tested
- Manual start used as a clue
- ATS and controller checked together
- Onsite across Gauteng
When the supply drops
Why doesn't my generator start when the power goes off?
Either the automatic system never asked the engine to start, or it asked and something blocked the start. Common causes are an ATS that sends no start signal, a controller left out of Auto, a battery or charger problem, a pressed emergency stop, a shutdown alarm, a wiring fault, a mains-sensing fault, or a fuel or starter fault that only shows once a start is requested.
The most useful clue is whether the engine starts from the panel in manual. If manual works and automatic does not, the engine is unlikely to be the first fault. If manual fails as well, we test the battery and the starter along with the switch.
We test the full sequence in order: the mains fails, the start request goes out, the engine cranks and runs, and only then does the load transfer. Proving one step does not prove the next, so we check every one.
Measured, not guessed
Battery charge between outages
A weak battery may manage a manual start and still fail the automatic sequence. We check that the charger keeps the battery floating at the right voltage, typically 2.25 V to 2.30 V per cell, or about 13.5 V to 13.8 V on a 12 V lead-acid battery (Battery University). A charger that falls short lets the battery run down while the set stands.
Fault guide
Generator not starting automatically: what it can mean and what to do
If your standby set starts by hand but not when the mains fails, the ATS signal, the controller mode or the battery is the usual cause. This guide separates what you can safely notice from what a qualified technician tests. One symptom never proves that a particular part has failed.
Symptom, likely cause and repair
Find the line closest to what you see. The cause is the most likely one, not a diagnosis: testing confirms it before any part is replaced.
| What you see | Likely cause | Usual repair |
|---|---|---|
| The mains fails and nothing happens | The controller is not in Auto, or a shutdown is latched | Controller repairs |
| Starts on the panel, never on its own | Mains sensing or the start signal from the transfer switch | ATS repairs |
| Tries to start on its own, then gives up | A weak battery or a fuel problem on the automatic attempt | Battery and charging repairs |
| Starts on its own but the building stays dark | The transfer switch is not moving the load | ATS repairs |
01
What you may notice
- The mains fails and the generator does not start
- It starts from the manual button but not on its own
- It starts automatically but the load does not transfer
- It attempts to start and gives up with an alarm
02
Possible causes
Any of these can produce the same symptom. Testing decides which one applies.
- The controller left in Manual or Off instead of Auto
- No remote-start signal from the changeover (ATS) or mains-sensing circuit
- An unreset alarm blocking automatic starts
- A weak battery that manages a manual start but not the automatic sequence
- Controller settings or timers changed
03
What you can safely check
Look and note only, from outside the canopy. Do not open panels, covers, fuel lines or the cooling system.
- Is the controller in Auto mode? Look at the display or mode lights.
- Is an alarm or warning showing?
- Does the set start from its manual start button, if you have been shown how to use it safely?
- Has anyone worked on the electrical board or changeover recently?
04
Stop using the generator and call if you notice
- A burning smell from the changeover or distribution board
- Breakers that trip when the changeover switches
- Any sign of mains and generator connected at the same time
If it is safe to reach, stop the generator with its normal stop control or emergency stop, keep people away, and call a technician.
05
What a qualified technician typically tests
These are technician checks, not steps to try yourself. Several involve live electrical measurement, fuel or pressurised systems.
- Mains-failure detection and the remote-start signal
- Controller mode, timers and alarm history
- Battery and starter under the automatic sequence
- Changeover operation and interlocks
06
Common repair categories
The repair follows the test result. These are the services this symptom most often leads to.
07
What to send when you book
- Your suburb and how we reach the generator
- Make, model and kVA from the data plate (a photo is ideal)
- Fuel type: diesel, petrol or gas
- Whether it starts manually
- A photo of the controller screen and the changeover panel label
08
Related faults and services
Not sure which symptom fits? Try the generator symptom finder.
Safety before you check anything
- Exhaust contains carbon monoxide, which you cannot see or smell. Run a portable generator outdoors only, away from doors, windows and vents, and never run any generator in a house, garage or other enclosed space.
- A standby generator set to automatic can start at any moment, when the mains fails or on its exercise timer. Keep the canopy closed and stay clear of fans, belts and the exhaust.
- Generator output, the changeover and the control panel can be live, and some parts hold stored electrical energy after shutdown. Leave panels, covers and wiring closed for us to open.
- The engine, exhaust and coolant stay hot after running. Never open a radiator or coolant cap on a hot engine.
- Do not refuel a running or hot generator. If you smell gas at a gas-fuelled set, do not operate switches; leave the area and contact your gas supplier.
Carbon monoxide guidance: US Consumer Product Safety Commission: Generators and engine-driven tools (carbon monoxide).
Send the details on WhatsApp
This opens WhatsApp with a short message already typed: brand, model, capacity, symptoms and suburb. Fill in what you know and send it. Blank lines are fine.
- The data-plate photo is added inside WhatsApp after the chat opens: tap the attachment or camera icon and choose the photo. A link cannot attach the photo for you.
- Take the photo only when the generator is switched off and has cooled down. Do not reach over or into a running or hot generator, and keep away from the exhaust.
- A standby generator set to automatic can start by itself when the mains supply fails. If you are not sure how it is set, photograph the plate from a distance or send a photo of the whole set instead.
Typical repair costs for this fault
Published ranges, last reviewed October 2026. The callout is R400 – R700 in business hours and R700 – R1,400 after hours, and it is waived if you accept the quote. Your written quote after diagnosis is the price that applies.
- Control panel repair or reprogramming
- R3,500 – R14,000
- Battery replacement
- R900 – R2,800
Step 9: book a diagnosis visit.
Related Pages
ATS, controllers and other start faults
- ATS Repairs The switch that should call for a start
- Controller Repairs Mode, alarms and the module
- Deep Sea (DSE) Controllers Auto start or AMF, and the sequence
- Generator Not Starting Will not start even in manual
- Not Switching Back The return half of the sequence
- Cranks But Won't Start The request arrived and it will not fire
- Generator Callouts Book the visit
- Standby Generator Maintenance Keep it ready between outages
Common Questions
Questions about generators that do not auto start
What does not auto starting mean?
It means your standby set does not start by itself when the mains supply fails, even though it may start by hand.
Is this the same as a generator that will not start at all?
No. If it also fails in manual, it has a general no-start fault. This fault sits in the automatic sequence.
It starts when I press the button. Why does the outage not start it?
Usually because the ATS is not sending a start signal, the controller is not in Auto, or an alarm is blocking the automatic path only.
Can a flat battery stop an automatic start?
Yes. A failed charger lets the battery run down between outages, so the set is dead when the mains drops.
There is an emergency stop pressed. Does that block auto start?
Yes. A pressed emergency stop or a latched shutdown holds off every start. Find out why it was pressed before anyone resets it.
The generator cranks when the power fails but does not fire. Where does that sit?
The start request arrived, so we look at fuel and the other reasons an engine cranks without firing. If that is the whole symptom, our cranks-but-won’t-start guide covers it.
Should I force the transfer switch?
No. Forcing a transfer switch or bridging live gear is dangerous. We test the sequence safely and never defeat a shutdown.
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
Tell us what happens when the mains fails
Does it do nothing, click, crank, or start only when you use manual? We are open 24/7 and arrive within 1 hour when your standby set lets you down.
- 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.