Carrier Streamline Scroll 69NT20-531-300 - Manual (Page 62)

5-3 T-309
CONDITION POSSIBLE CAUSE
REMEDY/
REFERENCE
SECTION
5.6 UNIT WILL NOT DEFROST PROPERLY -- Continued
Will not initiate defrost
Manual defrost switch defective Replace
Will not initiate defrost
manually Defrost temperature sensor open 4.9.5
Initiates but relay (DR) drops
out
Low line voltage 2.3
Initiates but does not defrost
Heater contactor or coil defective Replace
Initiates but does not defrost
Heater(s) burned out 6.15
Frequent defrost Wet load Normal
5.7 ABNORMAL PRESSURES (COOLING)
Condenser coil dirty 6.11
Condenser fan rotating backwards 6.12
High discharge pressure
Condenser fan inoperative 6.12
High discharge pressure
Refrigerant overcharge or noncondensibles 6.7.1
Discharge service valve partially closed Open
Suction modulation valve malfunction 6.20
Faulty suction pressure transducer Replace
Suction service valve partially closed Open
Filter-drier partially plugged 6.13
Low refrigerant charge 6.7.1
Low suction pressure Expansion valve defective 6.14 Low suction pressure
No evaporator air flow or restricted air flow 6.15
Excessive frost on evaporator coil 5.6
Evaporator fan(s) rotating backwards 2.3
Suction modulation valve malfunction 6.20
Suction and discharge pressures
tend to equalize when unit is
Compressor operating in reverse 5.14
tend to equalize when unit is
operating Compressor cycling/stopped Check
5.8 ABNORMAL NOISE OR VIBRATIONS
Compressor start up after an extended shutdown
Normal
Brief chattering when manually shut down
Normal
Compressor operating in reverse 5.14
Compressor Loose mounting bolts or worn resilient mounts Tighten/Replace Compressor
Loose upper mounting 6.8.1 step r.
Liquid slugging 6.14
Insufficient oil 6.9
Bent, loose or striking venturi Check
Condenser or Evaporator Fan Worn motor bearings 6.12/6.17 Condenser or Evaporator Fan
Bent motor shaft 6.12/6.17