Manitowoc Indigo Series Technician's Handbook page 268

HARVEST CYCLE DIAGNOSTICS QUIETQUBE ®
REMOTE CONDENSING UNIT
The headmaster control valve diverts the compressor
discharge gas to the ice machine receiver in the
harvest cycle. All refrigerant flow through the
condenser in the harvest cycle stops. Symptoms of a
headmaster valve that will not seat 100% closed
(completely bypass the condenser) in the harvest
cycle are:
• Freeze cycle suction and discharge pressure are
normal.
• The control board indicates safety limit #2. The
failure seems to be temperature related. Example:
The ice machine may function correctly at
temperatures above 32°F but fails at temperatures
below 32°F.
• Harvest cycle suction pressure is low.
• Harvest cycle discharge pressure is normal or
slightly low.
Procedure
1. Freeze cycle operation must be normal before
diagnosing the headmaster in the harvest cycle.
(Refer to Cycle Times/24 hr Ice Production/
Refrigerant Pressure Chart)
2. Allow the ice machine to run a normal freeze
cycle (do not initiate an early harvest cycle).
3. At the start of the harvest cycle feel the
compressor discharge line and the liquid line to
the ice machine receiver at the headmaster valve.
The temperature of both lines will be highest at
the beginning of the harvest cycle and then
decrease. Compare the lines 30 seconds into the
harvest cycle and then refer to Harvest Cycle
Headmaster Control Valve Failure List page 273.
268 Part Number Preliminary 6/11