S1800 Marine Model Ice Machines – Service Manual - Manitowoc Ice

Refrigeration System Section 7
Operational Analysis (Diagnostics)
GENERAL
When analyzing the refrigeration system, it is important
to understand that different refrigeration component
malfunctions may cause very similar symptoms.
Also, many external factors can make good refrigeration
components appear bad. These factors can include
improper installation, or water system malfunctions such
as hot incoming water supply or water loss.
The following two examples illustrate how similar
symptoms can result in a misdiagnosis.
1. An expansion valve bulb that is not securely
fastened to the suction line and/or not insulated will
cause a good expansion valve to flood. If a service
technician fails to check for proper expansion valve
bulb mounting, he may replace the expansion valve
in error.
The ice machine now functions normally. The
technician erroneously thinks that the problem was
properly diagnosed and corrected by replacing the
expansion valve. Actually, the problem (loose bulb)
was corrected when the technician properly
mounted the bulb of the replacement expansion
valve.
The service technician’s failure to check the
expansion valve bulb for proper mounting (an
external check) resulted in a misdiagnosis and the
needless replacement of a good expansion valve.
2. An ice machine that is low on charge may cause a
good expansion valve to starve. If a service
technician fails to verify the system charge, he may
replace the expansion valve in error.
During the replacement procedure, recovery,
evacuation and recharging are performed correctly.
The ice machine now functions normally. The
technician erroneously thinks that the problem was
properly diagnosed and corrected by replacing the
expansion valve.
The service technician’s failure to check the ice
machine for a low charge condition resulted in a
misdiagnosis and the needless replacement of a
good expansion valve.
When analyzing the refrigeration system, use the
Refrigeration System Operational Analysis Table. This
table, along with detailed checklists and references, will
help prevent replacing good refrigeration components
due to external problems.
7-4 Part Number 80-1634-3