conditioning system circuits should be loose or hot. If some connector is loose or the surface
temperature of connector felt by touching is relatively high (hot), the inside of connector is in poor
contact, which makes air conditioning system stop working or work in abnormal condition.
3. Check fault by listening
Listen carefully for abnormal noises of compressor and whether compressor is working normally to
identify whether no refrigeration or poor refrigeration of air conditioning system is caused by faults
of compressor or compressor control circuit.
4. Common Faults and Elimination Methods
(1) Air conditioning system is not refrigerating, both compressor and blower stop working.
1) Control circuit fuse protector is blown—after finding out causes, replace with fuse protector of
the same specification.
2) Disconnection of control line or earth wire—check whether each terminal or earth strap
connection is loose or disconnected, reconnect them firmly.
3) Damage of blower relay—Check whether blower relay coil is damaged and check the intactness
of contact terminal. If damage exists, repair or replace it.
4) Damage of electromagnetic clutch coil—check whether electric current exists in clutch coil. If no
electric current exists, repair or replace it.
5) Damage of electronic temperature controller—check whether thermal resistor temperature
sensor is damaged, and check whether thermal resistor characteristics are normal, then check the
amplifying part. If fault of temperature controller exists, repair or replace it.
6) Fault of pressure switch—inject 300KPa (G) refrigerant into refrigerating system. If refrigerating
system starts to work again, low-pressure switch is in normal condition; if not, fault of low-pressure
switch exists. Short connect the pressure switch. If the system starts to work, fault of the pressure
switch exists. Short-circuit method can also be applied to check high-pressure switch. Repair or
replace pressure switches with faults.
7) Blower stops working—check whether blower circuit is in normal condition, whether fan blades
are blocked and whether blower motor is damaged.
(2) Insufficient refrigerating capacity
1) Too little refrigerant—both high pressure and low pressure are relatively lower. Make leak
detection, repair and inject refrigerant again till pressure is back to normal;
2) Excessive refrigerant—both high pressure and low pressure are relatively higher and pressure
meter dithers severely. Get cooling medium back, re-vacuumize and inject refrigerant with definite
quantity;
3) Moisture exists in system—after air conditioner working for a period, low pressure becomes
vacuum, frost and ice plug appear on expansion valve, outlet air is not cold. Stop air conditioner
and restart it later. After air conditioner works normally for a short time, above faults appear again.
Inleak of damp air or moisture in refrigerant or refrigerant oil is too much. Replace drier and extend
vacuumizing time, fill in dry cooling medium and lubricants again;
4) Dirty matters exist in system—low pressure side appears to be in vacuum, pressure of high
pressure side is on the lower side, moisture condensation and frost appear on front and rear
pipelines of drier-receiver or expansion valve and outlet air is not cold. If the condition is not
improved after power off, the fault is dirty matter blockage. Replace drier-receiver and parts
blocked by dirty matters;
Compressor is damaged, inleakage exists—low pressure is over high while high pressure over low,
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