What does E01 mean on a Manitowoc ice machine?

Long freeze cycle — but the duration depends on your generation. On an Indigo it means the freeze reached 60 minutes; on an Indigo NXT it means 35 minutes. On both, six consecutive long freezes stop the machine. Common causes are scale, a dirty condenser or air filter, low refrigerant charge, or water supply problems.

What does E02 mean, and is it urgent?

Long harvest. It is far less urgent on an Indigo than on an Indigo NXT, which surprises people. An Indigo logs the fault at 3.5 minutes but keeps running until 500 consecutive long harvests. An Indigo NXT harvests to 7 minutes and stops after three. Same code, very different urgency.

My machine shows an alert but it is still making ice. Can I ignore it?

No, and this is the one that catches people. If the ice thickness probe or water level probe has failed, the machine enters Safe Operation Mode and keeps making ice from the timing of its last five good cycles — for 72 hours, then it switches to standby and stops. Check the event log for E19, E20 or E31. Ice coming out of the machine is not evidence that nothing is wrong.

How do I see the error codes?

On Indigo and Indigo NXT, go to Menu > Service > Event Log > View ELog. Each entry gives the code, when it first happened and how many times. Alerts appear on the fourth line of the Home screen and are cleared with the checkmark. Q and S Series machines have no display at all — a flashing Harvest light is the only indication, and it stores just the most recent safety limit.

My Manitowoc has stopped making ice for over an hour. Is it broken?

Possibly not. On Indigo NXT, a harvest that hits the 7-minute limit starts a water thaw cycle lasting about an hour, and the freeze cycle after it takes roughly 1 to 1.75 hours. That is more than two hours of no ice from a machine working exactly as designed. Check the display before booking a call-out.

How do I reset a Manitowoc ice machine?

On Indigo and NXT, press the power button so the display reads Off, then press it again for Making Ice. If a service fault stopped it, it restarts after a short delay; if it stops again, the condition has repeated and it needs diagnosing rather than resetting. Clear an alert with the checkmark, and clear the log from the Event Log menu. On Q Series there is no reset as such — a stored safety limit is erased automatically by 100 continuous harvests.

Ice machines · Manitowoc

Manitowoc ice machine error codes

Q: What cleaner can I use?

Only Manitowoc Ice Machine Cleaner (part 9405463) and Manitowoc Sanitizer (part 9405653). Never mix them, and never use high-pressure water jets. If the machine needs cleaning more often than every six months, Manitowoc’s own advice is to have the water quality tested rather than just cleaning more frequently — filtration costs less than repeat service calls.

Almost every page on this subject lists four codes. Manitowoc’s own technician handbook documents more than thirty — and the two everyone does list mean different things depending on which generation of machine you own.

Last reviewed November 2026

Before anything else

Isolate power before opening a panel. Refrigerant, sealed-system and mains work needs a licensed technician, and on a machine under warranty it generally has to go through an authorised servicer. Manitowoc also approves only its own cleaner (part 9405463) and sanitiser (part 9405653), and says never to mix them.

First: which generation?

Three families are still in service and they do not share a diagnostic system. Get this wrong and every number below is meaningless.

Generation	Models	How faults appear
Q / S Series	Q130 to Q450, S-series	No display and no codes. A safety limit is signalled by the Harvest light flashing
Indigo	I0300 to I1800	Full display. Event log E01–E34, plus Safety Limit #1 and #2
Indigo NXT	IDT, IYT, IRT, IDF, IYF, IDP, IBT, QuietQube	Display with alerts. Same code letters, different timings

The trap: E01 is not one fault

E01 is "long freeze" and E02 is "long harvest" on both Indigo generations. The durations are completely different, so the same code describes a different machine behaviour:

	Indigo	Indigo NXT
Max freeze before E01	60 minutes	35 minutes
Consecutive long freezes that stop the machine	6	6
Max harvest before E02	3.5 minutes	7 minutes
Consecutive long harvests that stop the machine	500	3

Read that last row twice. On an Indigo, a long harvest is logged but the machine keeps running for five hundred of them. On an NXT it stops after three. A technician applying NXT figures to an Indigo will chase a fault that is not urgent, and the reverse mistake means missing one that is.

The full event log, E01 to E34

From Manitowoc's Indigo technician handbook. Reach it on the machine at Menu > Service > Event Log > View ELog. Each entry shows the code, when it first occurred, and how many times.

Code	Meaning	What triggers it
E01	Long Freeze	Six consecutive 60-minute freezes. Machine stops, SL#1 light flashes
E02	Long Harvest	Three consecutive 3.5-minute harvests. Logged as SL#2; runs on until 500 occur
E03	Power Loss	Power interruption, stamped at power-up. Event only, no alarm
E04	High Condenser Temp	Liquid line too hot
E05	HPC Fault	High pressure cutout opened
E07	Starving TXV / Low Charge	Ten consecutive cycles where average T3 minus T4 exceeds 12°F
E08	TXV Fault	Dual-circuit, single-evaporator units
E09	Flood Evaporator 1	In the first 6 minutes of freeze, average T2 discharge falls below the previous 6 cycles
E10	Flood Evaporator 2	Dual-TXV, dual-circuit units
E11	Refrigeration Fault	Discharge does not rise 10°F and evaporator does not drop 10°F by 2 minutes into freeze
E12	Curtain Fault	Curtain open more than 12 hours while set to make ice
E15	Low Liquid Temp	Liquid line below 60°F for over a minute during freeze (low ambient)
E16	Remote Condenser Fault	Liquid line below 40°F or above 140°F for over a minute during freeze
E19	Ice Thickness Probe Fault	Probe frequency out of range — unplugged, or a microphone problem. Can trigger Safe Mode
E20	Water System Fault	High probe sensing without low; or evaporator outlet below −10°F at 6 minutes into freeze; or water probe satisfied at end of harvest. Can trigger Safe Mode
E21–E24	T1–T4 sensor issue	A thermistor's 6-second average outside valid range during pre-chill
E25–E27	Bin probe low / med / high	Bin level thermistor out of range for more than 10 continuous minutes
E28	AUCS	AUCS clean selected but no AUCS board detected. Event only
E31	Safe Mode entered	Event only — but see below, because this is the one that bites
E32–E34	RS485 comms, keyboard, display	Control hardware faults

E06, E13, E14, E17 and E18 are spares. E29 and E30 are USB events for engineering use.

Safe Mode: the 72-hour clock most owners never notice

This is the most important thing on this page, and almost nobody writes about it.

If the ice thickness probe or the water level probe fails, the machine does not stop. It enters Safe Operation Mode, logs E31, flashes an alert on the display, and keeps making ice using timed fill and freeze cycles based on the last five good cycles. After 72 hours it enters standby and switches off.

So the machine in front of you is producing ice, the bin is filling, everything looks fine — and there is a three-day countdown running that nobody has read, because the only sign is an alert icon. It will stop at some arbitrary hour, which in practice means the middle of service.

Two further details worth knowing:

It needs history. Safe Mode requires five completed cycles to copy. A machine that has never completed five — a new installation commissioned with the water off, say — simply shuts off instead.
It exits by itself. If the probe signal returns to normal, the control leaves Safe Mode automatically. That is also why the fault can come and go without anyone diagnosing it.

If you see an alert and the machine is still making ice, that is not a reason to relax. Check the event log for E19, E20 or E31.

Q and S Series: no display at all

Older Q-series machines have no screen and no codes. The Harvest light flashes when the machine has stopped on a safety limit. If it is not flashing, the machine did not stop for a safety limit, and you should be looking elsewhere.

Two quirks that cost people time:

Only one limit is stored — the last one exceeded. Earlier events are gone, so an intermittent problem leaves no trail.
It erases itself. A continuous run of 100 harvests automatically wipes the stored safety limit. Switching the toggle to OFF and back to ICE before that does not clear it, so if a machine has been running fine for a few days, the evidence has already deleted itself.

Before you call anyone: the thaw cycle

On Indigo NXT, if a harvest hits the 7-minute limit the machine starts a water thaw cycle — circulating, dumping and refilling for roughly an hour. The freeze cycle after that takes about 1 to 1.75 hours.

That is a machine sitting there making no ice for well over two hours while behaving exactly as designed. If you have just had a harvest problem, check the display and wait before paying for a call-out.

The ice thickness probe

This is Manitowoc's signature component and the cause behind E19, so it is worth knowing the numbers:

Target ice bridge thickness is 1/8" (3 mm), factory set.
To set the gap from scratch, place a 7 mm (9/32") drill bit between probe and evaporator, then fine-tune to a 1/8" bridge.
Clockwise increases bridge thickness, counterclockwise decreases it. One-third of a turn is about 1/16" (1.5 mm), so adjustments are smaller than people expect.
Check the bridge after a harvest, and confirm the probe wire is not restricting the probe's movement.
On a new machine, the shipping brackets must be removed before start-up.

Scale on the probe is a common cause of T3/T4 complaints. Manitowoc's remedy is to soak the probe in cleaning solution for 10 minutes and then sanitise it.

Testing a thermistor

If cleaning has not fixed an E21–E24 or a T3/T4 complaint, read the sensors at Menu > Services > Diagnostics > Temp Sensors. With power disconnected, measure resistance and replace the thermistor if it is more than 10% off the manual's value. An open thermistor reads around −22°F (−30°C); a shorted one reads about 475°F (246°C). Those two numbers alone identify most failed sensors.

What this costs

The average repair on a commercial ice machine was $708.44 in 2021 across all fault types, parts and labour included. Most of that is the visit, not the part.

What makes Manitowoc faults worth understanding before you call is how many of them are not really faults. E12 is a curtain held open — a full bin, or something leaning on it. A long harvest on an Indigo is logged five hundred times before the machine cares. A machine idle for two hours may be in a thaw cycle. And the single most common root cause behind T3/T4 complaints is scale, which a cleaning cycle fixes for the price of a bottle of cleaner.

What to tell the technician

Model and serial number, and which generation — Q/S, Indigo, or Indigo NXT. The timings differ, so this changes the diagnosis.
The event log, not just the current alert: code, first occurrence, and count. Menu > Service > Event Log > View ELog.
Whether E31 appears, because that means it has been running on Safe Mode history.
On a Q-series: whether the Harvest light is flashing, and roughly how long the machine has been running since, given the 100-harvest auto-erase.
Timed freeze and harvest durations.
When it was last cleaned and sanitised, and with what.

Maintenance Manitowoc actually specifies

Task	Interval
Full clean and sanitise	At least every 6 months
Condenser clean	At least every 6 months
Air filter (self-contained)	Monthly, mild soap and water
Preventative maintenance clean	Between the 6-month cleans, to clean the water flow path

Manitowoc adds a point most manufacturers leave out: if your machine needs cleaning more often than every six months, that is a signal to have the water quality tested rather than simply cleaning more. Frequent scaling is a water problem, and filtration is cheaper than repeated service visits.

A clean and sanitise cycle takes about 24 minutes each, and you should wait 20 minutes after refitting parts before running the sanitise step. Use only Manitowoc cleaner (9405463) and sanitiser (9405653), and never mix them — mixing produces a chemical reaction, not a stronger cleaner.