Generator locked out — what it means, and how to clear it safely
The question is never "how do I clear the lockout". It is what locked it out — and on most modern controllers that is displayed on the screen, one line above the word everyone reads.
Locked out is not a fault. It is a consequence.
Getting that the wrong way round is the most expensive mistake made on generator control panels. A locked-out set has already shut down on a protective alarm, and the controller has latched itself into a state where it will not restart until that alarm has been cleared and reset by a person. The lockout is the controller doing its job. The fault is whatever tripped underneath it.
The whole design, in one distinction
Warning, or shutdown?
Warning
The set keeps running
Something needs attention. The controller is telling you, not stopping you.
- Low fuel level
- Charge alternator failure
- Low coolant level, on some configurations
Shutdown
The set stops and latches
Something will damage the machine or endanger people. The controller stops the set immediately, latches the alarm so it cannot be lost, and refuses to restart.
- Displayed as locked out, shutdown or electrical trip
- Latching is deliberate — a set that quietly reset itself at 03:00 would keep restarting into the same fault until the bearings were gone
- It exists so a human has to look before the machine runs again
Deep Sea (DSE) panels are the most common controllers on UAE gensets; the 6000 and 7000 series, including the DSE7320 and DSE7320 MKII auto mains failure modules, show the latched alarm on the display and hold the module stopped. ComAp InteliLite modules and OEM panels from Caterpillar, Cummins, FG Wilson and Kohler all use the same principle with different vocabulary. Whatever the badge on the door, the logic is identical.
Capture this first
Read the alarm before you touch the reset button
Two things, in this order, before anything is cleared. Both cost nothing, and both are gone the moment you press reset.
1 · The alarm on the screen
- Photograph it before resetting
- Once you press reset it is gone
- "It said something about pressure, I think" is not a diagnosis anybody can work from
2 · The event log — the more useful one
- Most modern controllers hold a history of what tripped and when
- The alarm displayed is what tripped last. The log tells you what tripped first.
- On a cascading fault those are different alarms, and the difference is the whole job — a set showing under-voltage that logged low oil pressure ninety seconds earlier has a lubrication problem, not an electrical one
If the panel will show it, photograph the log too and send both to +971 50 767 9050. Interrogating event logs is one of the fastest ways to shorten a diagnosis.
Find your alarm
What is usually underneath a lockout
| Latched alarm | What it means, and what to do before resetting |
|---|---|
| Low oil pressure | Either genuinely low pressure or a failed sender. Check the oil level and condition. Do not reset and rerun to see if it repeats — if the pressure was real, bearing damage started on the first run. |
| High coolant temperature | Cooling system, ventilation, load, or a failed sender. Do not open a hot system, do not add cold water, do not restart until the cause is known. See generator overheating. |
| Overspeed | Governor, actuator or fuel rack. A set that has run away once will do it again, and an overspeed can throw parts. This is never a reset. |
| Under-speed / under-frequency | The engine could not hold speed. Load, fuel restriction or governor. See under and over frequency faults. |
| Under-voltage / over-voltage | Excitation, AVR, sensing, or genuinely wrong load conditions. See generator voltage problems. |
| Fail to start | Cranked for its configured attempts without reaching firing speed. See generator not starting. |
| Emergency stop | The mushroom button, or a break in the E-stop wiring loop. Find out why it was pressed before you release it. |
| Loss of magnetic pickup | The controller cannot see engine speed. The engine may have been running perfectly and been shut down by a blind controller. |
| Charge alternator failure | Usually a warning rather than a shutdown, but on some configurations it latches. Belt, alternator or excite wire. |
| ECU shutdown (red) | The engine's own ECU has commanded a shutdown and passed it over CAN. The panel is the messenger; the code lives in the ECU. See ECU warning lights. |
| Earth fault / electrical trip | A protection device has operated on the electrical side. Never reset this without finding the fault. |
| Failed to close / failed to open | A breaker or contactor did not confirm the position the controller commanded. |
Controller in Stop, not Auto
What you can safely check yourself
All of this is within reach of a competent site electrician or plant technician, and none of it requires opening a live enclosure.
The decision
When a reset is safe, and when it is not
Safe to reset
- A warning you have understood and dealt with.
- A low fuel alarm after the tank has been filled.
- An emergency stop you know the reason for, once released.
- A fault you have physically corrected and verified.
Not safe to reset
- Low oil pressure. High coolant temperature. Overspeed.
- Any earth fault or electrical trip.
- Any alarm with a burnt smell, smoke, a knock or a new mechanical noise alongside it.
- Any alarm you cannot explain. In every one of these the damage happens on the run after the reset, not the run before it.
A protection device that has operated three times is not being temperamental
The habit is familiar: a set locks out, someone resets it, it runs for a while, it locks out again, and by the third reset the alarm is treated as a nuisance rather than information. It is reporting a fault that is getting worse, and the reset is quietly consuming whatever margin the machine had left. Never bypass, strap out or defeat a protection device to keep a set running. If a set genuinely must run while a fault is investigated, that is a decision made by an engineer standing in front of it with instruments, with the risk understood and the run supervised — not a link fitted across a terminal.
It will not clear
Why some sets refuse to reset at all
Six usual reasons, when the controller will not clear even after the fault has been corrected.
- The fault is still presentMost modules will not accept a reset while the condition persists — an emergency stop still latched, a still-hot engine, a still-open breaker.
- The wrong reset sequenceSome modules require the set to be put into Stop before the reset is accepted.
- The E-stop loop is brokenSomewhere other than the button, so the controller still sees the circuit open.
- A second, hidden alarmPresent behind the one displayed. This is where the event log earns its keep.
- The controller itself has failedOr its DC supply is dipping. Rare, but it happens — diagnosed by proving the supply before condemning the module.
- The configuration has been changedA trip set wrongly, an input configured as a shutdown that should be a warning, or a timer so short the set trips itself. Sets that lock out repeatedly for no physical reason are surprisingly often configured to.
Panel-side work — controller faults, sensing and wiring repair, controller replacement — is on control panel diagnostics and AVR repair.
Twenty minutes that saves a rebuild
Verify the input before you believe the alarm
Prove the input. Then act on the alarm.
A low oil pressure shutdown means one of two things: the oil pressure was low, or the sender said it was. The only way to know is to measure the actual pressure with an independent mechanical gauge. Replace the sender because it was the cheapest thing to replace, and you have a set that will destroy its bearings on the next run. Strip the engine because the alarm said so, and you may have spent a great deal of money on a two-dirham sender. The same logic applies to temperature, speed and voltage alarms — it is the difference between fixing a generator and swapping parts at it.
Before you phone
When to call, and what to have ready
Call when the alarm underneath the lockout is on the do-not-reset list, when the set has locked out repeatedly, when you cannot identify what caused it, or when the diagnosis needs equipment you do not have — an independent pressure gauge, insulation testing, or the software to read a controller's configuration and history properly.
- Genset make, model and kVA
- Controller make and model
- A photograph of the alarm screen and the event log
- Running hours
- What changed before the fault
Send that to +971 50 767 9050 on WhatsApp. Most lockouts are identified from the alarm photograph before anyone travels, and if it is something you can safely put right yourself we will tell you so on the phone. Site currently without power: emergency generator repair. Planned work and quotations: jacob@abradiesel.com.
Common questions
Lockouts, answered
What does "generator locked out" mean?
A shutdown alarm has tripped and the controller has latched itself into a stopped state, refusing to restart until the fault is cleared and the alarm reset by a person. It is not a fault in its own right. Read the alarm displayed with it — that is the fault to fix.
How do I reset a generator that is locked out?
Read and photograph the alarm and the event log first. Establish what caused the shutdown and correct it. Then put the controller in Stop and press reset. If the alarm was low oil pressure, high coolant temperature, overspeed or any electrical trip, do not reset it at all until the cause is known and fixed — those are the ones where the damage happens on the next run.
Why will my generator not reset even after I press the reset button?
Usually because the fault is still present — most controllers will not accept a reset while the condition persists. Other common reasons are a still-latched emergency stop or a break in its wiring loop, a second alarm hidden behind the one on screen, the wrong reset sequence for that module, or a controller DC supply problem. The event log usually shows which.
Is it safe to keep resetting a generator that locks out repeatedly?
No. A protection device that operates repeatedly is reporting a fault that is getting worse, and each reset spends a little more of the machine's remaining margin. Two lockouts on the same alarm is the point to stop and diagnose rather than reset a third time.
What does "locked out" mean on a DSE 7320?
The same as on any other module: a shutdown alarm has latched and the controller will not permit a restart until it is cleared and reset. DSE 6000 and 7000 series modules display the causing alarm alongside the latched state and hold an event log — read both before resetting anything.
Can a locked-out generator be caused by the panel rather than the engine?
Yes. Failed senders, chafed wiring, poor earthing, a DC supply that dips during cranking, and trip settings configured wrongly all produce genuine-looking shutdowns on a healthy engine. That is exactly why the input should be verified with an independent instrument before anything is replaced — and why a set that locks out with no physical cause is often a configuration or wiring job rather than a mechanical one.
Set locked out and the site is off supply?
Photograph the alarm screen and the event log and send them with the genset and controller nameplates. Do not reset an alarm you cannot explain. Open 7 days, 07:00–20:00.