385 

 

1. The compressor efficiency is decreased.   

Check it or replace with a new 
compressor.  

The high pressure is low 
yet the the low pressure is 
high 

2. Opening of the expansion valve is too big.   

Adjust the opening of the expansion 
valve or replace with a new expansion 
valve.  

1. The low pressure increase fast after the power off- the 
system is ice blocked.   

Replace with a new liquid storage 
drying bottle.   

The high pressure is low 
yet the the low pressure is 
of negative pressure 

2. The low pressure increase slowly after the power off - 
the system is blocked.   

Clean the system.   

1. The inlet air filter is blocked.   

Replace with a new inlet air filter 
cartridge.  

2. The air duct is blocked.   

Clear the air duct.   

3. There is dirt on the evaporator surface.   

Clean the evaporator surface.   

The 
voltage is 
normal 

4.    The blasting motor is in sluggish operation.   

Check or replace with a new blasting 
motor.  

1.    Supply voltage of the entire car is unsteady.   

The air 
volume is 
insufficient 

The 
voltage is 
inadequate 

2.    The power ground is out of order.   

Check .   

The high pressure can only 
reach a certain value.   

1.    The clutch or the belt is slippery.   

Check or replace the clutch or the belt. 

1.  The evaporator temperature sensor is in poor 
condition.  

Replace the sensing head or check if its 
position is correct.   

2.  Harness and plug-in unit of the evaporator 
temperature sensor are in poor condition.   

Check  

3.    Too much refrigerant 

Discharge a portion of the refrigerant 

4.  Air capacity passing through the evaporator is 
inadequate.  

Inspect if the fan rotation speed is 
normal.  

The evaporator is frozen 

5. Failure expansion valve   

Replace it 

 

 
 

 

 

386 

No.290 Installation and Commissioning of the Air Conditioning   

Commissioning 

Inspect the 

leaking point 

Leak detection by 
nitrogen positive 
pressure 

Vacuumizing 

Fill in the refrigerant 

Watch the window until the filling volume 
is appropriate 

Leak 
detection 

Close the manifold pressure gauge and watch for 5 minutes without felling back
being occurred 

The liquid refrigerant can be filled from the high pressure side per the regulation 
before the system start-up; gaseous refrigerant must be filled from the low 
pressure side after the system start-up. 

Remain it for at least 72 hours after the vacuum degree is 745mmHg 

No felling back occurs when the filling pressure is 3.0Mpa 

 
 

 

 

387 

 

Cautions for installation safety 

·Installation staffs of air conditioning must wear protective glasses.   
·During the operation and the commissioning of the air conditioning unit, hands of the loading staffs shall be 
kept away from various fans and water tank fans.   
· The high pressure and low pressure pipes shall be checked carefully before charging the cooling medium to 
avoid the explosion.   
· Open flame is strictly prohibited to touch the refrigerant to avoid the choking caused by the toxic gas 
generated by the burning.   
· The radiator fin shall be taken care not to scuff the hand skin when the radiator is operated.   
· Metal ornament is strictly prohibited when the air conditioning is installed to avoid the injury caused by the 
short circuit.   
Treatment to the installation accident 
· If the refrigerant touches the eyes, a great deal cold water shall be used to flush the eye not less than 10 
minutes.  
· If a great deal of refrigerant is leaked and the skin is frostbite, the frostbite location must be warmed up and 
then the injury shall be sent to the hospital.   
Installation notice 
· Usage of the compressor oil.   
· Usage of the seal.   
· Installation of the pipeline:   
· The pipeline installation must be clean and dry; plugging material on the pipeline could be removed only 
when the pipe is installed.   
·R134a pipeline adopted by our company is of the sausage type sealing so the nut shall be tightened only afte
the pipeline connection is ensured to have been inserted totally; the nut must be tightened by hand and then by
two wrenches.   
·The refrigeration oil must be dripped before the screwed joint is connected to prevent the thread from 
stripping and ensure the sealing property.   

·Sharp transition is not permitted for the pipeline installation especially for the low pressure pipe installation. 

   

 

 

 

 

 

 

Incorrect (the pipeline should 
be put naturally) 

Correct 

 
 

 

 

388 

Special repair kit for air conditioning 
The special repair kit for air conditioning is composed of the magnetic thickness gauge, the gas leak tester, the 
spare gas bottle, the service valve wrench, the refrigerant filling valve, the filling hose gasket and the service 
valve gasket, etc. Above tools are special tools used to repair the vehicle air-conditioning. Tools in the kit shall 
be used as much as possible during the repair process to ensure the check quality.   
Usage of the refrigerant filling valve 
The filling valve is as Fig. 4-6 
1). Anti-clockwise rotate the filling valve handle until the valve needle is withdrawn.   
2). Install the filling valve on the refrigerant tank and anti-clockwise rotate the sheet nut until it reaches the top 
position, then clockwise rotate the refrigerant filling valve until the filling valve is embedded into the refrigerant 
sealing plug.   
3). Clockwise rotate the sheet nut to the end and fix the intermediate hose of the manifold pressure gauge into 
the connection of the filling valve.   
4). Tighten the sheet nut.   
5). Clockwise rotate the handle until the valve needle pierces into the sealing plug.   
6). Provided the refrigerant is to be filled, the handle shall be rotated anti-clockwise to uplift the valve needle 
and at the same time the hand valve on the manifold pressure gauge is opened.   
7). Provided it is to stop adding the refrigerant, clockwise rotate the handle so that the valve needle will enter 
into the sealing plug once again to play the sealing effect, and meanwhile close the hand valve on the manifold 
pressure gauge.   
Usage of the manifold pressure gauge 
The manifold pressure gauge is also called the manifold pressure meter, which is connected with the 
refrigeration system to carry out the vacuumizing, filling in the refrigerant and diagnosing the failure of the 
refrigeration system. Fig. 4-2 shows the structure of the manifold pressure gauge. It consists of the high 
pressure gauge, low-pressure gauge, manual low pressure valve, manual high-pressure valve, valve body, 
high pressure connection, low-pressure connector and refrigerant vacuumizing connector. During the 
operation, high and low pressure connectors are connected with high and low pressure fill in valves of the 
system respectively via the hose and the intermediate connector is connected with the suction pump or the 
refrigerant (HR134a) cylinder. The connector connecting the hose and the manifold pressure gauge could only 
be tightened by hand instead of by wrench, or else the connection thread may be damaged. Air inside the hose 
must be drained away during the usage. Detailed steps are as follows:   
1). When the manual low pressure valve is opened and the manual high pressure valve is closed, the low 
pressure line is connected with the intermediate pipeline and the low pressure gauge. At that time the 
refrigerant can be filled or discharged from the low pressure side, and meanwhile pressures at both the high 
pressure side and the low pressure side can be detected.   
2). When the manual low pressure valve is closed and the manual high pressure valve is opened, the pressure 
line is connected with the intermediate pipeline and the high pressure gauge. At that time the refrigerant can be 
filled or discharged from the high pressure side, and meanwhile pressures at both the high pressure side and 
the high-tension side can be detected.   
3). Detection to pressures at high and low pressure sides can be made when both the manual high pressure 
valve and the low pressure valve are closed.   

4). Refrigerant filling, vacuumizing and detecting to pressures at both the high pressure and low pressure 
sides can be carried out when both the manual high and low pressure valves are opened.