2. Take readings from pressure gauges under the following conditions.
- A) Air intake control switch in position "RECIRC" (air temperature in the air intake is 30-35°С).
- b) The engine operates at 1500 rpm.
- V) Fan switch in position "HI" (high speed).
- G) Temperature regulator in position "MAX COOL" (maximum cooling).
Note: Meter readings may vary slightly depending on ambient temperature.
Presence of water in the system
Pressure in the low pressure line changes from normal to vacuum (cooling works only intermittently, then stops working).
Cause: Water freezing in the expansion valve temporarily stops the cycle (blocks the circulation of the refrigerant). After defrosting, the system returns to normal.
Remedy:
- A) Replace receiver.
- b) Vacuum the water removal system.
- V) Charge the system with fresh refrigerant.
Lack of refrigerant
Reduced pressure in the entire system. Insufficient cooling. Bubbles in the service window all the time.
Cause: Lack of refrigerant, refrigerant leaks
Remedy:
- A) Check system for leaks
- b) Top up the refrigerant to the correct level.
Poor refrigerant circulation
Reduced pressure in the entire system. Frost on the pipeline from the receiver to the cooling unit. Insufficient cooling.
Cause: Poor refrigerant circulation due to clogged receiver
Remedy: Replace the receiver.
No cooling (refrigerant does not circulate)
Vacuum in the low pressure line, reduced pressure in the high pressure line (no cooling or cooling only intermittent; frost or condensate near the receiver or expansion valve).
Cause: The refrigerant does not circulate due to the presence of moisture or impurities in the system, or refrigerant leakage from the expansion valve.
Remedy:
- A) Check temperature sensitive tube and expansion valve.
- b) If the cause is contamination, then remove and clean the expansion valve with a jet of air. Replace valve if dirt cannot be removed
- V) Replace receiver.
- G) Vacuum and prime the system. If there is gas leakage from the heat sensitive tube, replace the expansion valve.
Too much refrigerant or insufficient condenser cooling
High pressure throughout the system (insufficient cooling), no bubbles in the service window, even when the engine is running at low speeds.
Causes:
- Insufficient circulation due to system overcharging.
- Clogged condenser fins or faulty condenser fan motor.
Remedy:
- A) Clean the plates.
- b) Check fan operation.
- V) If items "A" And "b" completed, check the amount of refrigerant.
Presence of air in the cooling system
High pressure throughout the system (insufficient cooling); low pressure hot line; bubbles in the service window.
Cause: Air in the system (it is possible that the system was not evacuated before charging).
Remedy:
- A) Replace receiver.
- b) Check the absence of contamination and the amount of compressor oil.
- V) Vacuum and prime the system.
Incorrect installation of the expansion valve / malfunction of the heat-sensitive tube
High pressure throughout the system (insufficient cooling, frost or heavy condensate on the low pressure pipe).
Cause: The temperature sensitive tube is not adjusted, the expansion valve is incorrectly installed.
Remedy: check the heat sensitive tube; if it is working, then check the expansion valve. Lure faulty parts.
Compressor failure
In the low pressure line - increased pressure, in the high pressure line - reduced pressure. No cooling.
Reason: Compressor defective (valve leaks or worn parts).
Remedy: Repair or replace the compressor.