York Y9USC-09 B5R - Compressor Not Stopping; Insufficient Cooling or Heating; Unit Stops After Startup; No Cooling or Heating Output

Service manual
18
The compressor not to
stop even the room
temp. has got to the
setting temperature.
Thermostat
Check and replace if the thermostat is damaged.
Air filter
Clean or replace if restricted.
Vent. door
Close if open.
Unit undersized
Determine if the unit is properly sized for the area to be cooled or heated.
Condenser and Evaporator
Clean or replace if restricted.
Fan motor
Check the fan capacitor and replace if not within +/-10% of manufactures rating.
Room structure
Take proper measures to make the door and windows sealed well if gap is found.
Air flow
Clean or remove if any barrier is found to block the inlet/outlet wind flow of the unit.
Sunlight
Add a awning if the condenser is exposed to the sunlight.
Less refrigerant
Check the tubes for reasons of leakage. Recycle the refrigerant, correct the leakage
points and recharge.
Capillary tube
Regulate the flow if capillary tube and make the evaporating temperature
appropriate if the evaporator is frosted. Replace if blocked. Repair joint if leaking.
Compressor
The inlet and outlet valve of the compressor is damaged, making the low pressure
connected with the high pressure. The refrigerating system can not produce high
pressure and low pressure. Replace the compressor after checking for the reason.
Heat sources
Reduce if too many.
reverse valve
The seal in valve is damaged, making the low pressure connected with the high
pressure. The refrigerating system can not produce high pressure and low pressure.
Replace the reverse valve after checking for the reason.
Insufficient cooling or
heating.
Drainage
The drainage is blocked. It will increase the efficiency in cooling mode, but will cause
the condenser to frost in heating mode.
Refrigerant
The amount of the refrigerant is too much, making the compressor load too big.
Recycle and recharge the refrigerant after checking for the reason.
Stop instantly after
startup.
Compressor
The compressor is seized. Replace after checking for the reason.
No power
Check the voltage. Call an electrician if no within the limit.
Wiring
Check the terminals. Repair and correct if loose.
Temperature setting
Check and adjust the thermostat.
Main switch setting
Check and adjust the main switch setting.
Reverse valve wire
Check the resistance of reverse valve wire. Replace the wire if short, open or
damaged.
No cooling or heating.
Reverse valve
If the reverse valve is blocked, the heating mode will not perform. Replace the
reverse valve after checking the reason.