Rancilio Espresso Machine Warning W04: No Flowmeter Signal, Group 4
W04 on a Rancilio Classe 11 reads No signal from flowmeter group 4: the control receives no flowmeter signal from group 4. The manual gives no operator remedy, so contact a Rancilio service technician. The other three groups should keep working normally.
Medium: one group cannot dose by volume, while the rest of the machine works.
- Code
- W04
- Maker
- Rancilio
- Equipment
- Espresso machines
- Applies to
- Classe 11 USB / Xcelsius
What does Rancilio error code W04 mean?
A four-group Classe 11 has a flowmeter on every group. Each one counts the water that passes through, and the control uses the count to stop the shot at the programmed volume. When group 4 runs and no pulses come back, the control records W04 No signal from flowmeter group 4. Without the count, group 4 cannot dose by volume, so its shots may run long, stop early or not stop at all. The other three groups continue as normal, so you can keep serving on them while you wait for a visit. The reasons are the usual ones for a flowmeter: scale that holds the turbine still, a loose or damaged cable, or a water path that is blocked so nothing flows. The manual lists the warning without an operator remedy, and the signal has to be measured to tell these apart.
Affected models and control systems
This applies to the Classe 11 USB and Xcelsius espresso machines. We read the List of errors in the 07/2014 edition of the manual.
Code numbers and their meaning can change between control generations. We match the full model and control before acting on a code.
What you may notice
- W04 on the display
- Group 4 shots too long, too short or never ending
- Volume on group 4 not matching the programmed dose
- Groups 1, 2 and 3 dosing as usual
Possible causes
Likely causes — what usually sits behind error code W04 on this control. A technician confirms which one it is before any part is replaced.
- Group 4 flowmeter turbine seized by scale
- Flowmeter plug worked loose at group 4
- Water line to group 4 clogged
- Flowmeter cable damaged by heat or rubbing
Safe checks before calling for service
- Run a manual shot on group 4 and check that water comes out at a normal rate.
- Look under the group for leaks or damp connectors.
- Serve from the other three groups until the machine is checked.
- Do not unplug parts while the machine is powered.
- Contact a Rancilio service technician and tell them how group 4 behaves on programmed shots compared with manual ones.
How a technician diagnoses error code W04
- Read W04 and the error history to see how often it appears.
- Confirm water flows through group 4 on a manual shot.
- Inspect the flowmeter connector and the wiring back to the board.
- Check the flowmeter for scale or debris.
- Measure the flowmeter signal at the board while water flows.
- Replace the flowmeter or cable and calibrate group 4 dosing.
- Measuring a signal at the board means working in the open machine, near line-voltage parts.
- Dosing is calibrated with the machine's own settings after a flowmeter is replaced.
- A clogged water path means taking the group apart with the boiler cool and depressurized.
How error code W04 differs from similar codes
W01 to W03 are the same warning for groups 1 to 3. E16 is a short on the supply that powers all the flowmeters.
Technical reference
- Maker documentation
- Rancilio owner support
- Edition
- REV:-- 07/2014
- Models / control
- Classe 11 USB / Xcelsius
- Section
- List of errors, pp. 27-29
- Checked
- October 2026
We use the maker's document to read the code and do not reproduce it. Always confirm the complete model and control before applying these steps.
Related Rancilio espresso machine error codes
Can I keep using the machine with W04 showing?
Yes, normally, on groups 1 to 3. The warning names only group 4.
Which machines can show W04?
Only four-group machines. Smaller machines have no group 4.
Is W04 the same as E16?
No. E16 is a short on the flowmeter supply, while W04 means no signal is coming back from group 4.
Need help with Rancilio error code W04?
A technician confirms the cause on site and gives you the price in writing before any work starts.