Diagnosis of system failures (Mitsubishi Pajero 4)

Contents: Checking by direct visual inspection…⤓ Tactile Failure Testing ⤓ Hearing test ⤓ Checking the amount of refrigerant ⤓

Checking by direct visual inspection and observation

In the event of a failure or deviation from the normal functioning of the air conditioning system, certain external signs of malfunction occur. In this case, the check can be carried out by direct inspection and observation.

1. Carefully check all tubes for breaks or cracks, as well as the outer surfaces of the condenser and evaporator for oil stains and streaks. If grease is found on the surface of the above parts, it is possible to assume that a leak has formed in the system and attempt to pinpoint its location by testing with soapy water at the following key points:

1) Connectors for connecting tubes and valves.
2) Hoses and hose connectors.
3) Compressor seal, front and rear covers, sealing gaskets, etc.
4) Scratched, deformed areas on the surface of the condenser, evaporator.

2. Checking through the inspection window: The amount and condition of the refrigerant can be checked through the inspection window of the line.

Before starting observation, start the engine, turn on the air conditioning system, and maintain the engine at high idle speed (1000-1500 rpm) for 5 minutes, then check the state of the refrigerant circulation through the inspection window:

1) If the refrigerant flow is uniform and bubbles sometimes form in it, then the system condition is normal.
2) If the refrigerant is transparent and no air bubbles are formed in it, then either there is no refrigerant in the system at all, or too much refrigerant has been added. If the air vents become cool, the system is functioning normally; if not, a refrigerant leak may have formed.
3) Too many bubbles in the flow is a sign of insufficient refrigerant.

3. Check the line: check for loose connections.

Tactile Failure Testing

1. Check the high pressure line of the air conditioning system.

Turn on the air conditioner, let the compressor run for 10-20 minutes, touch the high-pressure line of the air conditioning system with your fingers in the direction of compressor outlet → condenser → dryer → expansion valve inlet, the temperature should change from hot to warm.

If some parts become too hot, this may be due to insufficiently effective heat dissipation; if these parts are cold, this indicates a blockage in the line, lack of refrigerant, failure or inefficient operation of the compressor.

2. Check the low pressure line of the air conditioning system.

Turn on the air conditioner, let the compressor run for 10-20 minutes, touch the low-pressure line of the air conditioning system with your fingers in the direction from the condenser to the compressor inlet, the temperature should change from cool to cold.

If the parts are not cool, and if frost forms in certain places, the normal functioning of the system is disrupted.

3. Check the temperature difference at the compressor outlet.

Turn on the air conditioner, let the compressor run for 10-20 minutes, touch the compressor with your fingers at the inlet and outlet points, you should feel a noticeable difference between the temperatures of the low and high pressure lines.

If the temperature difference is not noticeable, this indicates that there is no or insufficient refrigerant in the system.

4. Circuit check: Manually check electrical connectors for secure connection, looseness or heating.

The article was taken from the website: mitsubishiman.ru

If the connectors are loose or hot, the malfunction of the air conditioning system may be caused by poor conductivity of the connectors.

Hearing test

Listen carefully to the system after switching it on to check for the sound of the compressor running and the absence of extraneous noise during its operation, which will allow you to determine where the cause of insufficient cooling efficiency is located - in the compressor or in the line.

Checking the amount of refrigerant

Method: visual inspection through the inspection window of the air conditioning system line.

№	Signs	Refueling volume	Methods of elimination
1	Bubbles are constantly forming	Blocked	1. Check for gas leaks, repair if necessary. 2. Add refrigerant until the bubbles disappear, then add another 50 g of refrigerant.
2	There are no bubbles	No refrigerant, system blocked or too much refrigerant	See description of operations 3) and 4).
3	No difference is observed between the compressor inlet and outlet	No refrigerant	1. Check for gas leaks, repair if necessary. 2. Add coolant until the bubbles disappear.
4	Significant difference between compressor intake and exhaust	Normal or too much refrigerant	See description of operations 5) and 6).
5	The flow immediately clears up after turning off the air conditioner	Too much refrigerant	1. Drain the refrigerant from the system to the specified volume.
6	After turning off the air conditioner, bubbles are first formed, then the flow becomes clearer	Fine	-

Note: If the ambient temperature is higher than normal, a slight gas bubble will be observed in the inspection hole with a normal amount of refrigerant.

Verification conditions: