5--3
T-334
CONDITION
POSSIBLE CAUSE
REMEDY/
REFERENCE
SECTION
5.6 UNIT WILL NOT DEFROST PROPERLY - Continued
Will not initiate defrost
manually
Manual defrost switch defective
Replace
Defrost temperature sensor open
4.10.5
Initiates but relay (DR) drops
out
Low line voltage
2.3
Initiates but does not defrost
Heater contactor or coil defective
Replace
Heater(s) burned out
6.13
Frequent defrost
Wet load
Normal
5.7 ABNORMAL PRESSURES (COOLING)
High discharge pressure
Condenser coil dirty
6.8
Condenser fan rotating backwards
6.9
Condenser fan inoperative
6.9
Refrigerant overcharge or noncondensibles
6.3 /6.4
Discharge service valve partially closed
Open
Suction modulation valve malfunction
6.18
Low suction pressure
Faulty suction pressure transducer
Replace
Suction service valve partially closed
Open
Filter drier partially plugged
6.11
Low refrigerant charge
6.3 /6.4
Expansion valve defective
6.12
No evaporator air flow or restricted air flow
6.13
Excessive frost on evaporator coil
5.6
Evaporator fan(s) rotating backwards
6.15.3
Suction modulation valve malfunction
6.18
Suction and discharge pres-
sures tend to equalize when unit
is operating
Compressor operating in reverse
5.14
Compressor cycling/stopped
Check
5.8 ABNORMAL NOISE OR VIBRATIONS
Compressor
Compressor start up after an extended shutdown
Normal
Brief chattering when manually shut down
Compressor operating in reverse
5.14
Loose mounting bolts or worn resilient mounts
Tighten/Replace
Loose upper mounting
6.5.1 step t.
Liquid slugging
6.12
Insufficient oil
6.6
Condenser or Evaporator Fan
Bent, loose or striking venturi
Check
Worn motor bearings
6.9/6.15
Bent motor shaft
6.9/6.15
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