The Nuova Simonelli Aurelia throws a handful of faults that show up again and again in Bay Area cafes. Most trace back to a few root causes. Knowing which is which helps you decide whether to limp through a slow morning or shut the machine down and call someone.
The most common faults
No steam or weak steam pressure. Scale buildup in the boiler or steam wands is the leading cause. The Aurelia’s boiler is sized for high-volume work, so it tolerates neglect longer than a home machine, but calcium eventually catches up. If steam pressure has been slowly dropping over weeks, that’s almost certainly scale. A sudden drop is more likely a pressure stat going out of range or a solenoid stuck partially closed.
Group head not dispensing, or dispensing slowly on one group. Flow restrictors and shower screens accumulate coffee oils and fine grounds faster than most owners expect. On volumetric models like the Aurelia Wave and Aurelia II, the flow meter can also fail, which throws off volumetric dosing and causes inconsistent or stopped flow. If backflushing didn’t fix it, the solenoid valve on that group is next on the list.
Machine not reaching temperature, or running too hot. The Aurelia uses PID-controlled heating. If the temperature probe drifts or fails, the boiler chases a ghost setpoint. Running too cool and running too hot are both symptoms of the same failure mode. You’ll sometimes see a fault on the display; sometimes it just brews bad shots with no warning.
Water on the drip tray or under the machine. Group head gaskets wear out. On a high-volume machine they can go fast. If the leak shows up during extraction and tracks to the group head area, that’s the likely culprit. Leaks from underneath, near the boiler or plumbing fittings, are a different problem and need proper diagnosis before anyone starts taking things apart.
Pump noise, or pump running constantly. A loud rattling vibration pump usually just needs replacement. A pump that runs constantly, even with nothing being extracted, points to a pressure switch or flow meter fault. That needs diagnosis before you swap parts.
How a tech diagnoses these
A good tech starts with a pressure gauge on the group head and a temperature check at the boiler. On the Aurelia, the technician service menu gives direct access to sensor readings, so you can see what the PID is measuring versus what it should be without disassembling anything. That alone narrows the field quickly.
Flow meter faults usually show up as erratic shot volumes. The tech will cycle the group a few times and watch the counter. Solenoid valves get checked with a multimeter, then physically pulled if the reading looks off.
For leaks, the tech pressurizes the system and traces water paths. A lot of leaks on the Aurelia are from fittings or the expansion valve, not the group head, and those are easy to miss if you’re only looking at the obvious spots.
Descaling gets done with a controlled acid wash, not just a tablet. On a commercial boiler, the process takes time and has to be done right or you risk damaging internal components.
What you can do yourself
Backflushing with a blind filter and detergent on a regular schedule is something any barista can handle. Pulling and cleaning shower screens and filter baskets is low-risk and worth doing consistently. These keep the machine running well between bench services.
Beyond routine cleaning, call a tech. Group head gasket replacement looks simple but involves working on a pressurized commercial machine, and the risk of a mistake (system not fully depressurized, wrong torque on the carrier, reusing a bad screen) is real. Solenoid work, boiler service, and PID calibration all need the right tools and real familiarity with the Aurelia’s plumbing layout. Getting it wrong costs more in downtime and secondary damage than the service call would have.
Call us
If the machine is losing pressure, running at the wrong temperature, leaking anywhere other than a drain you’ve already identified, or throwing a fault you can’t clear, stop trying to work around it. High-volume espresso machines fail harder when pushed through symptoms.
Diagnostics can take up to a week; most repairs run 3–4 weeks. That is exactly why we recommend preventive maintenance: a maintained machine does not sit in a repair queue for a month.