5-3
T-292
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
4.10.5
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
6.13
Frequent defrost
Wet load
Normal
5.7 ABNORMAL PRESSURES (COOLING)
Condenser coil dirty
6.8
Condenser fan rotating backwards
6.9
High discharge pressure
Condenser fan inoperative
6.9
High discharge pressure
Refrigerant overcharge or noncondensibles
6.4
Discharge service valve partially closed
Open
Suction modulation valve malfunction
6.18
Faulty suction pressure transducer
Replace
Suction service valve partially closed
Open
Filter-drier partially plugged
6.11
Low refrigerant charge
6.4
Low suction pressure
Expansion valve defective
6.12
Low suction pressure
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
Compressor operating in reverse
5.14
sures 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
6.5.1 step t.
Liquid slugging
6.12
Insufficient oil
6.6
Bent, loose or striking venturi
Check
Condenser or Evaporator Fan
Worn motor bearings
6.9/6.15
Condenser or Evaporator Fan
Bent motor shaft
6.9/6.15
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Summary of Contents for 69NT40-531 Series
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