Carrier 50HX Installation, Start-Up, And Operating Instructions Manual page 35

SYMPTOM
Head pressure too low
Excessive suction pressure
Suction pressure too low
Compressor runs but
outdoor fan does not
IFM does not run
IFM operation is intermittent
IFM (048–060) runs when
it should be off
IFM–Indoor Fan Motor
Table 14—Troubleshooting Chart (Cont'd)
CAUSE
Low refrigerant charge
Restriction in liquid tube
(Heat) Outdoor coil frosted
(Cool) High Heat load
Reversing valve hung up or leaking internally
Refrigerant overcharged
(Cool) Dirty air filter
(Heat) Outdoor coil frosted
Low refrigerant charge
Metering device or low side restricted
(Cool) Insufficient coil airflow
(Cool) Temperature too low in conditioned area
(Cool) Outdoor ambient below 40°F
Filter-drier restricted
NC (normally closed) contacts on defrost board
open
Blower wheel not secured to shaft
Insufficient voltage at motor
Power connectors not properly sealed
Water dripping into motor
Connectors not firmly sealed
Motor programmed with a delay profile
With thermostat in "off" mode, the voltage on
G, Y1, Y2, W with respect to common, should be
1/2 of actual low voltage supply
35
REMEDY
Check for leaks, repair and recharge
Remove restriction
Move timer on control board to 30 minutes
between defrost cycles
Check for source and eliminate
Replace valve
Recover excess refrigerant
Replace filter
Move timer on control board to 30 minutes
between defrost cycles
Check for leaks, repair and recharge
Remove source of restriction
Increase air quantity
Check filter–replace if necessary
Reset thermostat
Install low-ambient kit
Replace
Check condition of relay on board
Replace if necessary
Properly tighten blower wheel to shaft
Determine cause and correct
Connectors should snap easily; do not force
Verify proper drip loops in connector wires
Gently pull wires individually to be sure they are
crimped into the housing
Allow a few minutes for motor to shut off
If measured voltage is more that 1/2, the thermostat
is incompatible with motor. If voltage is less than
1/2, the motor has failed