Verification procedure
1. Connect the measuring manifold to the air conditioning system.
2. Check the system status under the following conditions:
- A) The air temperature at the evaporator inlet is 30-35°C.
- b) The frequency of rotation of the crankshaft of the engine is 2000 rpm.
- V) Air conditioning included.
- G) Temperature control switch: in the maximum cooling position.
- d) Heater fan switch: in high speed position.
Method for determining the relative humidity of the air.
Presence of a small amount of moisture and air in the system
The pressure in the low pressure line and the high pressure line is normal (slight air cooling). The pressure in the low pressure line does not change in the operating range of the thermal switch (position "ON" And "OFF").
Cause: Presence of air or moisture in the system.
Remedy:
- A) Check the system for leaks.
- b) Pump out the refrigerant from the system.
- V) Repair any leaks found.
- G) Replace receiver dryer.
- d) Evacuate the system for 30 minutes or more.
- e) Charge the system with coolant.
- and) Check system performance.
The presence of a significant amount of moisture in the system
The pressure in the low pressure line and the high pressure line is correct. Hot air is supplied to the passenger compartment at a high ambient temperature.
Reason: accumulation of moisture in the system.
Remedy:
- A) Pump out the refrigerant from the system.
- b) Replace receiver dryer.
- V) Evacuate the system for 30 minutes or more.
- G) Check the refrigerant level in the system (overcharge).
- d) Check system performance.
Thermal switch failure
The pressure in the low pressure line and the high pressure line is correct. The compressor turns on and off at high frequency when there is no proper conditions in the low pressure line.
Cause: Faulty thermal switch.
Remedy:
- A) Stop the engine and turn off the air conditioner.
- b) Replace thermal switch. Make sure that the location of the new thermal switch is exactly the same as the one that was replaced (relative to evaporator fins).
- V) Check system performance.
Thermal switch defect
The pressure in the low and high pressure lines is correct. The pressure in the low pressure line increases (switch-on pressure too high).
Cause: Faulty thermal switch.
Remedy:
- A) Turn off the air conditioner and turn off the engine.
- b) Replace or repair thermal switch (make sure the wiring is correct to avoid short circuits).
- V) Check system performance.
Insufficient amount of refrigerant in the system
The pressure in the low pressure line and the high pressure line is slightly below normal (slight air cooling).
Cause: There is not enough refrigerant in the system.
Remedy:
- A) Check the system for leaks.
- b) Pump out the refrigerant from the system.
- V) Repair any leaks found.
- G) Check compressor oil level.
- d) Evacuate the system for 30 minutes or more.
- e) Charge the system with coolant.
- and) Check system performance.
Very little refrigerant left in the system (leaks)
The pressure in the low and high pressure lines is below normal. Hot air is supplied to the cabin.
Cause: There is very little refrigerant in the system.
Remedy:
- A) Check the system for leaks.
- b) Check the compressor O-ring surface carefully for leaks.
- V) Pump out the refrigerant from the system.
- G) Check compressor oil level.
- d) Evacuate the system for 30 minutes or more.
- e) Charge the system with coolant.
- and) Check system performance.
Expansion valve blocked (closed)
The pressure in the line of low pressure and high pressure is below normal (slight air cooling, frost or dew on the expansion valve tubes).
Cause: Expansion valve is clogged, filter is clogged or the sight glass of the receiver-drier is defective.
Remedy:
- A) Pump out the refrigerant from the system.
- b) Disconnect the inlet pipe from the expansion valve, remove and check the filter.
- V) Clean or replace the filter, connect the inlet pipe.
- G) Evacuate the system for 30 minutes or more.
- d) Charge the system with coolant.
Clogged high pressure pipes
The pressure in the line of low pressure and high cooling is below normal (slight cooling of the air, frost or dew on the high-pressure pipes and the pipes are cold).
Reason: narrowing of the section of the high-pressure line pipes.
Remedy:
- A) Pump out the refrigerant from the system.
- b) Replace receiver dryer, high pressure pipes or other defective parts.
- V) Evacuate the system for 30 minutes or more.
- G) Charge the system with coolant.
- d) Check system performance.
Compressor failure
The pressure in the low pressure line is above normal, the pressure in the high pressure line is below normal. The compressor makes extraneous sounds during operation.
Cause: Compressor failure.
Remedy:
- A) Remove the compressor and install plugs on its fittings.
- b) Disassemble the compressor and check its parts.
- V) Check compressor oil level.
- G) Replace receiver dryer.
- d) Check system performance.
Capacitor Abnormal Condition (overload)
The pressure in the low and high pressure lines is above normal. Hot air is supplied to the cabin. The high pressure pipes are very hot.
Cause: defective condenser or its electric fan.
Remedy:
- A) Check the condition and fastening of the condenser fan.
- b) Check the condenser tube fins for damage or blockage.
- G) Check the correct installation of the capacitor.
- V) Check the refrigerant level in the system (overcharge).
- G) Check system performance.
Presence of air and moisture in the system
The pressure in the low and high pressure lines is above normal (slight air cooling).
Reason: a large amount of air and moisture in the system.
Remedy:
- A) Pump out the refrigerant from the system.
- b) Replace receiver dryer.
- V) Evacuate the system for 30 minutes or more.
- G) Charge the system with coolant.
- d) Check system performance.
Expansion valve stuck (open)
The pressure in the low and high pressure lines is above normal (hot air is supplied to the passenger compartment, frost or dew on the evaporator tubes).
Cause: Expansion valve malfunction.
Remedy:
- A) Pump out the refrigerant from the system.
- b) Replace the expansion valve, making sure that there is no contamination on the contact surface.
After installation, check that the valve is securely fastened.
- V) Evacuate the system for 30 minutes or more.
- G) Charge the system with coolant.
- d) Check system performance.