Diagnostics - Air Cooled - Scotsman MVP456 Service Manual

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DIAGNOSIS
No ice
Problem
No power to unit
No power to controller
Shut down on maximum
water fill time
Shut down on maximum
freeze time
Shut down on maximum
freeze time
Likely Cause
Power disconnected
replace, restart and check
Transformer open
Water shut off
Water leak
Air filters clogged
Dirty condenser
Restricted location, intake air too hot
Ice thickness sensor dirty or
disconnected
Water distributor dirty
Inlet water valve leaks through
during freeze
Connected to hot water
Incomplete harvest
High pressure cut out opened
Fan motor pressure control open
Fan motor not turning
Water pump not pumping
Pump hose disconnected
Compressor not operating
Low refrigerant charge
Hot gas valve leaks through during
freeze
Thermostatic expansion valve
bulb loose
Thermostatic expansion valve
producing very low or very high
superheat
Compressor inefficient
Probable Solution
Check breaker or fuse. Reset or
Replace transformer
Restore water supply
Check purge valve, curtain,
sump, pump hose
Clean air filters
Clean condenser
Have machine moved
Check ice thickness sensor probe
Remove and clean water distributor
Check inlet water valve
Check for bleed thru from / missing
check valve in building water supply
Check harvest system
Check fan motor pressure control,
check fan motor, check controller
using test mode
Check fan pressure control
Check fan motor, check fan blade,
check controller using test mode
Check pump motor, check controller
using test mode
Check hose
Check compressor contactor,
check controller using test mode
Check compressor start components
Check compressor voltage
Check compressor windings
Add some refrigerant and restart unit.
If cycle time improves, look for leak.
Check hot gas valve for hot
outlet during freeze
Check bulb
Check evaporator superheat,
change TXV if incorrect
Check compressor amp draw, if low and
all else is correct, change compressor
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