Carrier VECTOR 1550 Series - Page 259

62-61753-21
10-7
INDICATION/
TROUBLE
POSSIBLE CAUSES
REFERENCE
SECTION
10.4.6 Defrost Cycle Malfunction
Will not initiate defrost
automatically
DTT is above 40°F (4.4°C)
Cool Box Down
Loose terminal connections
Tighten
Air sensing tubes defective or disconnected
Check
Defrost air switch (DAS) defective or out of calibration
8.6.13
Will not initiate defrost manually
Microprocessor defective
Replace
Loose terminal connections
Tighten
DTT2 is above 40°F (4.4°C)
Cool Box Down
Unit has been running less than 15 seconds
Try again
Initiates but does not defrost
Heater contactor or coil defective
Replace
Heater(s) burned out
8.7.1
Frequent defrost
Defrost air switch (DAS) defective or out of calibration
8.6.13
Wet load
Normal
10.4.7 Abnormal Pressure
High discharge pressure
Condenser coil dirty
8.6.3
Condenser fan rotating backwards
Check Wiring
Condenser fan inoperative
Check
Refrigerant overcharge or noncondensibles
8.5.4/8.5.5
Discharge service valve partially closed
Open
Suction modulation valve malfunction
8.6.7
Low discharge pressure
Compressor worn or damaged
8.6.1
Low suction pressure
Suction service valve partially closed
Open
Filter-drier partially plugged
8.6.5
Low refrigerant charge
8.5.4
Expansion valve defective
9.4.11
No evaporator air flow or restricted air flow
9.4.10
Excessive frost on evaporator coil
9.4.6
Evaporator fan(s) rotating backwards
8.7.2
Suction modulation valve malfunction
8.6.7
Liquid line service valve partially closed
Open
High suction pressure
Compressor worn or damaged
8.6.1
Expansion valve defective
9.4.11
Suction and discharge
pressures tend to equalize
when unit is operating
Compressor worn or damaged
8.6.1
10.4.8 Abnormal Noise
Compressor
Loose mounting bolts
Tighten
Worn bearings
8.6
Liquid slugging
9.4.11
Condenser or evaporator fan
Loose or striking shroud
Check
Bearings defective
8.7.2
Bent shaft
8.7.2
Water pump belt
Cracked or worn
replace