373 

 

2).The evaporator is frosting;   

Frosting on the sedan A/C evaporator can be treated according to 
the following aspects:   
1).The thermo expansion valve is in abnormal operation: replace the 
thermo expansion valve;   
2).The evaporator is deficiency in draught: find out the reason and 
eliminate it;   
3). Thermo sensitive resistance of the temperature controller is in 
incorrect mounting position, so it is incapable of sensing the surface 
temperature of the surface temperature. Install the thermo sensitive 
resistance per correct position;   
4). Thermo sensitive resistance of the temperature controller is out 
of service so that the compressor can not stop; uninterrupted 
refrigeration will lower down the surface temperature of the 
evaporator. When the temperature is below 0℃, water vapor in the 
air flowing through the evaporator will be frosted on external surface 
of the evaporator: replace the thermo sensitive resistance;   
5).Design temperature of the temperature controller thermostat is 
over low that causes surface temperature of the evaporator below 
0℃ to frost: replace the thermostat;   

3)The evaporator assembly is 
blocked 

3) The ice block is caused by the moisture in the system and the 
dirty block is caused by the impurities such as the aluminium chips in 
the system; result of the ice block is that the evaporator is not cool 
sometimes, while the result of the dirty block is that the evaporator is 
not cool or is inadequate in the cooling volume: eliminate the 
moisture or the impurities.   

 

4)The thermo expansion valve 
is blocked or leaked;   

4).Constant malfunction of the thermo expansion valve: power head 
(gas phase head) of the thermo expansion valve is leaked that 
causes inadequate opening or incapable of being opened of the 
thermo expansion valve, thus the evaporator is not cool or is 
inadequate in cooling volume: replace the thermo expansion valve. 

1).There has dirt on the 
condenser flat pipe and the 
heat emission fin, which will 
reduce the heat transfer 
capability and increase the high 
pressure in the refrigeration 
system;  

Clean out dirt and impurities on the flat pipe and the heat emission 
fin;  

2).There is impurity blockage
on the condenser heat 
emission fin;   

Purge them with compressed air;   

3).The condenser heat 
emission fin is of flexural 
deformation;  

Calibrate it with the nipper pliers and replace the condenser if it is 
severe;  

Condenser 

4).The condenser is leaking;   

Replace the condenser 

1)Dry reservoir assembly is 
blocked;  

The block reason is the pulverizing of the drier as well as too many 
impurities in the system; the phenomena is that the high pressure is 
increased and there has apparent temperature difference between 
inlet and outlet of the dry reservoir assembly: replace the dry 
reservoir;  

Dry reservoir   

2)Filter screen inside the dry 
reservoir assembly is damaged; 

Thermo expansion valve maybe blocked so that the a/c will not 
refrigerate: replace the dry reservoir and check the thermo 
expansion valve;   

 
 

 

 

374 

1).The hose is aging damaged;  Replace damaged hose assembly;   

2).The connection is loose;   

Retighten the connection or replace the hose assembly;   

3).The connection thread is 
damaged;  

Replace the hose assembly;   

Pipeline assembly 

4).O seal ring is damaged;   

Replace O seal ring. The above failures will cause the refrigerant 
leaking;  

1).Wire of the blower or the fan 
is broke off;   

Reconnect the fan wire;   

2).Motor of the fan or the 
blower is damaged 

Replace the blower or the fan;   

3). Fuse of the blower or the fan 
is blown out or the switch is in 
bad contact;   

Check and replace the fuse, eliminate the switch bad contact;   

4).Governing resistance of the 
blower is damaged;   

Replace the governing resistance;   

Blower and condenser 
fan 

5).The fan blade is battered 

Replace the condenser fan (the above failure will cause deficiency in 
fan draught or no draught of the fan so that the high pressure will be 
abnormally high; deficiency in the blower draught or no draught of 
the blower will cause the evaporator to frost, deficiency in heating air 
or no heating air);   

 
 

 

 

375 

Diagnoses flow of air-conditioning system constant malfunction 

 

 

 
 

 

 

376 

Solution to auto a/c Constant malfunction: Auto air-conditioning system of Vision and Leading 
models are provided with failure self-diagnostic function. Some basic failures can be checked by 
the self checking function. In addition, we have enumerated some familiar failure symptoms and 
treatment processes, according to which you can find out the failure reasons and help your 
clients to solve the problems. 

No.273 Vehicle temperature sensor is in poor condition   

(code display 01)   

 

 

 

No.274 The vehicle exterior temperature sensor is in poor condition; 

(code display 02)   

 

 

The a/c controller is in poor condition 

B3 and B2 metal plug-in card inside B plug are in 
poor contact with the controller socket; 

1. Harness or metal plug-in connected with B3 and b2 is in 
poor condition;   
2. The vehicle temperature sensor is in poor condition. 

Test the ohmic value between B3 and B2 of B plug at the harness end with the meter 

Pull out B plug behind the control panel 

Power on and test if the voltage between B3 and B2 is0.5V≤Vi≤4.8V 

Yes 

Vehicle interior temperature sensor 

Is the ohmic value between 500 and 
100K? 

Yes 

No 

B2 

B3 

The a/c controller is in poor condition 

A12 and A11 metal plug-in card inside A plug are in 
poor contact with the controller socket; 

1. Harness or metal plug-in unit connected with A12 and A11 is 
in poorcondition;   
2. The vehicle exterior temperature sensor is in poor 

condition. 

Test the ohmic value between A12 and A11 of A plug at the harness end with the 
meter 

Pull out A plug Aehind the control panel 

Power on and test if the voltage between A12 and A11 is 0.5V≤Vi≤4.8V 

Yes 

Vehicle exterior temperature sensor 

Is the ohmic value between 500K and 
100K? 

Yes 

No 

A11 

A12 

A/C controller 

No