Note t
| Temperature of refrigerant circuit components should be equal to ambient temperature (the pressure will deviate from the values in the table if individual components of the refrigerant circuit are warmer or colder). |
t
| On the absolute pressure scale, 0 bar corresponds to an absolute vacuum. The normal ambient pressure corresponds to 1 bar absolute. On the scales of most pressure gauges, 0 bar corresponds to an absolute pressure of 1 bar (can be seen from -1 bar mark below 0). |
t
| Pressure can be measured in various units: 1 MPa (megapascal) is equivalent to 10 bar gauge pressure, or 145 psi; 1 bar absolute pressure is the same as 0 bar gauge pressure, which is roughly equivalent to atmospheric pressure. |
The pressure in the refrigerant circuit is lower than indicated in the table. |
Not enough refrigerant in circuit |
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| Determine refrigerant circuit leaks → Chapter. |
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| Check high-pressure safety valve. |
If the high-pressure safety valve has blown off: |
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| Check actuation of the radiator fans. |
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| Check for constricted refrigerant line and hose cross-sections caused by inadequate bending radii. |
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| Check refrigerant pipes and hoses for external damage. |
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| If no fault is found, clean refrigerant circuit (flush with refrigerant R134a → Chapter or blow out with compressed air and nitrogen → Chapter). |
The pressure in the refrigerant circuit corresponds to that indicated in the table or is higher. |
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| Set air conditioning system to maximum cooling output. |
Note If the air conditioner compressor is not driven when the engine is running or the regulating valve is not actuated: |
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| Establish and eliminate the cause e.g. by interrogating the air conditioner event recorder. |
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| Observe test requirements. |
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| Check the power supply for the air conditioning system magnetic clutch -N25-. If this is OK, service the magnetic clutch. |
Note t
| If the low-pressure switch has been removed to connect the air conditioner service station, jumper the electrical connections in the relevant connector for pressure measurement. |
t
| The air conditioner compressor is driven by the engine via the air conditioning system magnetic clutch -N25-. |
t
| Continuation of testing depending on design of refrigerant circuit → Chapter |
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