Carrier 50HS018 Installation, Start-Up And Service Instructions Manual page 31

Table 11 — Cooling and Heating Troubleshooting Chart (cont)
SYMPTOM
Excessive head
pressure.
Head pressure too low.
Excessive suction
pressure.
Suction pressure too
low.
Compressor runs but
outdoor fan does not.
CAUSE
Dirty air filter
Dirty indoor or outdoor coil
Refrigerant overcharged
Air in system
(Heat) Indoor air restricted or recirculating
Indoor or outdoor air restricted or
air short-cycling
Low refrigerant charge
Compressor valves leaking
Restriction in liquid tube
(Heat) Outdoor coil frosted
(Cool) High heat load
Compressor valves leaking
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
Field-installed filter-drier restricted
Normally closed contacts on defrost board open
Replace filter.
Clean coil.
Recover excess refrigerant.
Recover refrigerant, evacuate system, and recharge.
Determine cause and correct.
Determine cause and correct.
Check for leaks, repair and recharge.
Replace compressor.
Remove restriction.
Move timer on control board to 30 minutes
between defrost cycles.
Check for source and eliminate.
Replace compressor.
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.
31
REMEDY