A compressor that stays silent at the start of the day keeps the whole workshop waiting. In many cases the cause is simple and can be found in a few minutes. Here are the checks to make, in order, before calling a technician.
Safety first: do not dismantle anything while powered. Any work inside the electrical cabinet is for an electrician or our service team.
1. The compressor may simply be waiting
A modern compressor stops by itself when the set pressure is reached and restarts automatically when it drops. If the receiver and network are still under pressure, it is normal for it not to start. Look at the pressure gauge: if the pressure is above the restart point, open a tap or use a tool, and the machine should start again.
2. Is the power getting through?
- Breaker or fuses on the compressor's line: a breaker that tripped overnight is common after a storm or power cut.
- Main switch of the machine in the right position.
- Controller screen off: power is not reaching the machine.
- Three-phase compressor: a missing phase or reversed phase order (after electrical work, for example) prevents starting or triggers an alarm. Our screw compressors up to 22 kW run on 380 V three-phase: the check is for an electrician.
3. Is the emergency stop pressed?
The red mushroom button stays pressed until it is released, usually by turning it. After releasing it, you often need to acknowledge the fault on the controller before restarting.
4. What does the controller say?
If the screen shows an alarm, write down the exact message. The most common:
- temperature fault: the machine got hot and is protecting itself (see compressor overheating);
- phase or voltage fault: a power supply problem;
- service reminder: on some machines, a very overdue service can block operation;
- inverter fault on a variable speed model.
Do not reset an alarm over and over: if it comes back at every restart, the cause is still there.
5. Is it too cold?
A compressor in an unheated room may refuse to start in very cold weather: the oil thickens and some machines are protected against starting at low temperature. The room must stay frost-free. See compressor room installation.
6. On a piston compressor
In addition to the points above, check the pressure switch (the small box that controls starting) and the belt. A motor that hums without turning may come from an unloader valve that does not vent the compressor head: call service.
When to call service
If power is getting through, the emergency stop is released and the pressure is low, but the machine still will not start, or if an alarm comes back at every attempt, make a request from the warranty and service page. Have the model, serial number, hour meter and displayed message ready. While waiting for the repair, a hire compressor can keep the workshop running.
Other symptoms are covered in our compressor troubleshooting guide.