Manitowoc Ice Machine Error Code E31: Safe Mode Active
E31 notes that a Manitowoc Indigo ice machine has entered safe mode because the ice thickness probe or the water level probe has failed. It is log-only with no alarm, but safe mode is a short-term cover. Watch whether the ice looks thinner or thicker than usual, and call us.
Medium: the machine runs but ice quality can drift until the probe is repaired.
- Code
- E31
- Maker
- Manitowoc
- Equipment
- Ice machines
- Applies to
- Indigo series (non-NXT) control board, Event Log (Service menu > Event Log > View ELog)
What does Manitowoc error code E31 mean?
On Manitowoc Indigo ice machines without the NXT display, E31 notes that the machine has entered safe mode. The ice thickness probe or the water level probe has failed, so the board is making ice on historical cycle data. It is log-only, with no alarm. The idea behind safe mode is to keep the machine producing while a probe is out, by repeating the cycle timing it remembers from earlier. That works for a while, but it cannot follow changes in water temperature or supply, so ice size and quality can drift in the meantime. Staff may see slabs that are thin one day and thick the next. The display text for the entry is E31. The documented causes are the ice thickness probe reading, the water level probe reading, wiring and connectors at both probes, and scale buildup on the probe tips. A technician cleans, tests and replaces whichever probe has failed.
Affected models and control systems
Manitowoc Indigo series cubers with the non-NXT control board (Service menu > Event Log > View ELog). E31 relates to E19 (ice thickness probe) and E20 (water system).
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
- Ice size changing from batch to batch
- Slabs thinner or thicker than usual
- No alarm on the machine
- The E31 line in the Event Log
Possible causes
Listed in Manitowoc's documentation
- Ice thickness probe reading
- Water level probe reading
- Wiring and connectors at both probes
- Scale buildup on the probe tips
Other likely causes — what usually sits behind error code E31 on this control. A technician confirms which one it is before any part is replaced.
- Hard-water scale on a probe tip that lets the reading drop out of range
- A probe lead damaged when the evaporator was cleaned
- A water supply that varies, which exposes the weakness of timing-based cycles
Safe checks before calling for service
- Watch whether the ice looks thinner or thicker than usual.
- Make sure the water supply valve is open.
- Do not pull on probe wires.
- Call us, and write down how thick the ice looks.
How a technician diagnoses error code E31
- Read the Event Log for E31 and check for E19 or E20 entries.
- Inspect both probes, their wiring and connectors.
- Clean scale from the probe tips.
- Test each probe's signal on the control board.
- Replace the probe that fails and confirm the machine leaves safe mode.
- Safe mode hides which probe failed, so the control board data has to be read to find it.
- Probe signals are read at the board, in the line-voltage area.
- Running long in safe mode can waste water and produce poor ice.
How error code E31 differs from similar codes
E31 is the result of a probe failure, whereas E19 and E20 report the failing reading itself.
Technical reference
- Document
- Indigo Series Technician's Handbook 000014794 5/17, "Event Log" p.87-91
- Maker documentation
- Manitowoc owner support
- Edition
- Part Number 000014794 5/17
- Models / control
- Indigo series (non-NXT) control board, Event Log (Service menu > Event Log > View ELog)
- Section
- Event Log: code list p. 87, Event Log Detail table pp. 88-91 (Service menu > Event Log)
- 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 Manitowoc ice machine error codes
Can I keep running the machine in safe mode?
For a short time. Ice quality can drift, so call us soon.
Will E31 clear itself?
Only when the failed probe works again. Scale cleaned off a probe sometimes does it.
Is safe mode the same as E19?
No. E19 reports the thickness probe signal. E31 reports that the machine is now running on stored data.
Need help with Manitowoc error code E31?
A technician confirms the cause on site and gives you the price in writing before any work starts.