Manitowoc Ice Machine Safety Limit 2: Harvest Light Flashes 2 Times

What does Manitowoc Safety Limit #2: harvest light flashes 2 times mean?

On Manitowoc S-model, Q QuietQube and Indigo boards, two flashes of the harvest or safety limit light mean Safety Limit #2. In the harvest stage, warm refrigerant releases the slab so it can drop into the bin. The board allows this a set time, and when harvest reaches 3.5 minutes, or 7 minutes on quad-evaporator S models, it stops waiting and returns to freeze. After 500 long harvests in a row the machine stops, or after three on Q boards with a black microprocessor. Ice may release slowly beforehand, with the slab clinging to the plate. So the pattern is the opposite of Safety Limit #1, which is about freezing too slowly: here the problem is releasing the slab. The documented causes are a harvest valve that does not pass hot gas through the plates, scale on the evaporator plate that holds ice in place, an ice thickness probe at the wrong position, and a water inlet or dump valve that leaves water behind.

Affected models and control systems

S-model machines and Q QuietQube and Indigo boards; the pattern is read from the harvest or safety limit light. Newer controls use different codes.

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

• Light flashes twice
• Slab clinging to the plate after harvest
• Ice dropping slowly or in pieces
• Machine stopping after repeated long harvests

Possible causes

Listed in Manitowoc's documentation

• A harvest valve that fails to pass hot gas through the plates
• Scale on the evaporator plate that holds ice in place
• An ice thickness probe set at the wrong position
• A water inlet or dump valve that leaves water behind

Other likely causes — what usually sits behind Safety Limit #2: harvest light flashes 2 times on this control. A technician confirms which one it is before any part is replaced.

• Hard-water scale that has built up between cleanings and bonds ice to the plate
• A harvest valve coil that is weak and opens only part way
• A dump valve that drips and leaves water on the plate during harvest

Safe checks before calling for service

How a technician diagnoses Safety Limit #2: harvest light flashes 2 times

1. Count the flashes and confirm Safety Limit #2.
2. Watch a harvest and time how long the slab takes to release.
3. Check the harvest valve operation and the hot gas reaching the plate.
4. Inspect the plate for scale and the probe for position.
5. Check inlet and dump valves for leaking after the cycle.

How Safety Limit #2: harvest light flashes 2 times differs from similar codes

Two flashes is a harvest that ran long, the opposite of Safety Limit #1, which is a freeze that ran long.

Technical reference

Document

S Model Technician's Handbook 8014793 6/18 p.55; Q 80-0099-9 6/11 p.135

Maker documentation

Manitowoc owner support

Edition

Part Number 8014793 6/18

Models / control

S-model and Q QuietQube, Indigo boards

Section

Safety Limits, pp. 55-56 (single and quad evaporator models) and pp. 69-76 (quad evaporator machines); no event/error code table. The Q QuietQube 80-0099-9 6/11 p.134 reference in our title is a different document, not in this PDF.

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.