Manitowoc J250 Service Manual page 128

Section 7
Final Analysis
Before totaling the four columns, be sure to analyze
all detailed charts, checklists, and other references to
eliminate external causes which may make a good
refrigerant component appear bad.
The column with the highest number of check marks
identifies the refrigeration problem. Refer to the
appropriate heading below.
COLUMN 1 - HOT GAS VALVE LEAKING
Normally, a leaking hot gas valve can be repaired
with a rebuild kit instead of changing the entire valve.
Rebuild or replace the valve as required.
COLUMN 2 - LOW ON CHARGE/
TXV STARVING
Normally, a starving expansion valve only affects the
freeze cycle pressures, not the harvest cycle
pressures. A low refrigerant charge normally affects
both pressures.
Verify the ice machine is not low on charge before
replacing an expansion valve. To verify:
1. Add refrigerant charge in 2 to 4 oz. increments as
a diagnostic procedure to verify a low charge. If
the problem is corrected, the ice machine is low
on charge. Find the refrigerant leak.
The ice machine must operate with the nameplate
charge. If the leak cannot be found, proper
refrigerant procedures must still be followed
Change the liquid line drier. Then, evacuate and
weigh in the proper charge.
2. If the problem is not corrected by adding charge,
the expansion valve is faulty.
On dual expansion valve ice machines, change only
the TXV that is starving. If both TXV's are
starving, they are probably good, and are being
affected by some other malfunction, such as low
charge.
Refrigeration System
COLUMN 3 - TXV FLOODING
A loose or improperly mounted expansion valve bulb
causes the expansion valve to flood. Check bulb
mounting, insulation, etc., before changing the valve.
On dual expansion valve machines, the service
technician should be able to tell which TXV is
flooding by analyzing ice formation patterns. Change
only the flooding expansion valve.
COLUMN 4 - COMPRESSOR
Replace the compressor and start components.
To receive warranty credit, the compressor ports must
be properly sealed by crimping and soldering them
closed. Old start components must be returned with
the faulty compressor.
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