Abnormal Pressures (Cooling) - Carrier 69NT40--541--200 TO 299 Operation And Service

CONDITION
5.6 UNIT WILL NOT DEFROST PROPERLY - -Continued
Frequent defrost

5.7 ABNORMAL PRESSURES (COOLING)

High discharge pressure
Low suction pressure
Suction and discharge pres-
sures tend to equalize when unit
is operating
5.8 ABNORMAL NOISE OR VIBRATIONS
Compressor
Condenser or Evaporator Fan
5.9 CONTROLLER MALFUNCTION
Will not control
POSSIBLE CAUSE
Wet load
Condenser coil dirty
Condenser fan rotating backwards
Condenser fan inoperative
Refrigerant overcharge or noncondensibles
Discharge pressure regulator valve defective
Discharge service valve partially closed
Suction modulation valve malfunction
Suction service valve partially closed
Filter-drier partially plugged
Low refrigerant charge
Expansion valve defective
No evaporator air flow or restricted air flow
Excessive frost on evaporator coil
Evaporator fan(s) rotating backwards
Discharge pressure regulator valve defective
Suction modulation valve malfunction
Heat exchanger defective
Compressor valves defective
Compressor cycling/stopped
Loose mounting bolts
Worn bearings
Worn or broken valves
Liquid slugging
Insufficient oil
Bent, loose or striking venturi
Worn motor bearings
Bent motor shaft
Defective Sensor
Defective wiring
Fuse (F1, F2) blown
Stepper motor suction modulation valve circuit malfunction
5-3
REMEDY/
REFERENCE
SECTION
Normal
6.10
6.11
6.11
6.7.1
Replace
Open
6.18
Open
6.13
6.7.1
6.14
6.15
5.6
6.16.3
Replace
6.18
Replace
6.8
Check
Tighten
6.8
6.8
6.14
6.8.6
Check
6.11/6.16
6.11/6.16
6.23
Check
Replace
6.18
T-317