369 

 

A/C compressor fails to start

Fuse, electric appliance element 
and relay are in trouble 

Malfunction of low pressure 
switch 

Malfunction of temperature 
controller 

High pressure switch 

The electromagnetic clutch can not be 
sucked together 

The refrigerant is 
leaking 

The compressor bearing is damaged or oil 
shortage 

The electromagnetic 
clutch can’t work 

The compressor is of piston 
seizure 

Overhaul or replace 

Replace 

Overhaul or replace 

Overhaul or replace 

Overhaul or replace 

Overhaul 

Replace 

Replace 

Overhaul or replace 

Short circuit of ECU   

Replace the ECU 
assembly 

Normal 

Abnormal

Abnormal

Unable to suck

Abnormal

Abnormal

Leaking

Damaged

Cylinder sticking 

Abnormal

Abnormal

 
 

 

 

370 

 

No. 270 The A/C control mechanism is hard to operate   

Malfunction 
symptom 

Cause Solution 

Manipulating key of the control 
mechanism and rocker on the shell 
body are heavy 

1).Manipulating key of the control mechanism and rocker on the shell 
body are heavy: spread lubrication oil at the sliding part of each 
revolving member.   

The A/C control 
mechanism is 
hard to operate 

The air throttle is ineffective in 
rotation 

2).The air throttle is ineffective in rotation: repair the air throttle.   

 

 

 

No. 271 The A/C evaporator is frosting   

Malfunction symptom 

Cause 

Solution 

The thermo expansion 
valve can’t work 

1).The thermo expansion valve is in abnormal operation: replace the 
thermo expansion valve;   

.Thermo sensitive 
resistance of the 
temperature controller is 
mounted in incorrect 
position 

3). Thermo sensitive resistance of the temperature controller is 
mounted in incorrect position, so it is incapable of sensing the surface 
temperature of the evaporator. Install the resistance in correct position; 

Malfunction of thermo 
sensitive resistance of 
the temperature 
controller  

4). Thermo sensitive resistance of the temperature controller fails so 
that the compressor can not stop; uninterrupted refrigeration will lower 
down the surface temperature of the evaporator. when the temperature 
is below 0 degree, water vapor in the air flowing through the evaporator 
will be frosting on external surface of the evaporator: replace the 
thermo sensitive resistance;   

The A/C evaporator is 

frosting during the operation 

Temperature of the 
temperature controller 
thermo sensitive 
resistance is set too low 

5).Temperature of the temperature controller thermo sensitive 
resistance is set so low, causing surface temperature of the evaporator 
below 0 degree to frost: replace the thermo sensitive resistance;   

 

The A/C control mechanism is hard to 

operate 

Manipulating key of the control mechanism 

and rocker on the shell body are heavy 

The air throttle is ineffective in 

rotation 

Overhaul 

Overhaul 

Normal 

Heavy 

Blocked 

 
 

 

 

371 

 

The a/c evaporator is frosting 

The thermo expansion valve is in 
abnormal operation 

The evaporator is deficiency in draught 

Thermo sensitive resistance of the 
temperature controller is in incorrect 
mounting position 

Thermostat of the temperature controller is out of 
service 

Design temperature of the temperature 
controller thermostat is over low 

Replace 

Overhaul 

Re-mount 

Replace 

Replace 

Normal

Normal

Correct

Normal

Abnormal

Deficient

Incorrect 

Abnormal

Abnormal

 
 

 

 

372 

No. 272 Constant malfunction and solution of A/C components   

Spare parts name 

Constant malfunction 

Preclusion method 

A/C relay 

1).The contact is superficial charring;   
2).The relay coil is burnt out;   
3).The spring leaf is damaged and incapable of 
sucking;  

1).Connection check: bridge a wire at the suction position 
of the relay. If the compressor or the fan is in normal 
operation after the bridging, it means there is failure in the 
relay;  
2) Displacement method check: replace into a new relay 
of the same type and specification to make the judgment 
of the original relay. When replacing the damaged relay, it 
shall adopt the relay of the same model and specification 
and the relay position shall not be changed randomly;   

1).Cylinder sticking and cylinder scoring of 
compressor; the link rod is breakout; the pulley
does not rotate or is hard to rotate; there has 
abnormal sound;   
2).Valve leaf and valve plate of the compressor 
is damaged and there has abnormal sound;   
3).The compressor sealing gasket is breakdown 
that result in coalition between high and low 
pressures; high pressure is the same as the low 
pressure;  
4).The compressor shaft seal is leaked that 
causes large leakage of the refrigerant;   

Replace into a new compressor of the same model;   

5).Pulley bearing is damaged. Ultra large belt 
tension will generate too much radial bearing 
force, and the suction cup will be seized with the 
pulley thus damage the bearing;   

Replace the electromagnetic clutch and adjust the belt 
tensioning force;   

6).Coil of the electromagnetic clutch is short or 
broken so that the suction can not be generated; 
7).Clearance between the suction cup and the 
pulley is too small that causes the sticking or the 
seizure between the suction cup and the belt 
surface, or even the pulley charring;   
8).Fuse of the electromagnetic clutch is blown 
out;  

Replace the electromagnetic clutch;   

Compressor 

9). The electromagnetic clutch is slipping; 
suction between the pulley and the suction cup 
is inadequate that causes the slippage;   

Reason of insufficient suction and its preclusion method: 
(1).The electromagnetic clutch is insufficient in the power 
supply voltage: recharge the battery;     
(2).A/C relay is in poor contact: check the relay and 
replace it if anything wrong with it.   
(3).There has too much refrigerant or the compressor is 
of piston seizure that causes excessive load; discharge 
the surplus refrigerant or replace the compressor;   
(4).The electromagnetic clutch has slipping sound caused 
by the belt slippage; re-tension the belt;   

Evaporator 

1).The evaporator is leaking that causes the 
shortage of refrigerant or no refrigerant; the 
result is that the evaporator is insufficient in the
cooling volume or does not refrigerate.   

Replace the evaporator assembly or the evaporator.