The air conditioning system does not cool (Step 3 – Base Table A)

The table below shows the normal operating pressure values for the air conditioning system, which occur when the aforementioned initial conditions are configured. If the pressure values are not achieved, it must be assumed that there is an error in the air conditioning system.

Outdoor
temperature °C
Compressor with suction pressure regulator (V)
(Example: Harrison V5)
Compressor constant displacement (F)
(Example: SD 7H15, SS121DS1, etc.)
R134a R134a R134a
LP (bar) HP (bar) LP (bar) HP (bar) LP (bar) HP (bar)
min. max. min. max. min. max. min. max. min. max. min. max.
15.5 1.5 2.3 9.5 13.0 0.5 3.0 9.5 13.0 0.5 3.0 8.5 12.0
21.0 1.5 2.3 12.5 17.5 0.5 3.0 12.5 17.5 0.5 3.0 10.5 17.5
26.5 1.5 2.3 14.0 20.5 0.5 3.0 14.0 20.5 0.5 3.0 12.5 19.0
32.0 1.5 2.5 16.0 24.0 0.5 3.5 16.0 24.0 0.5 3.5 14.0 22.0
38.8 1.5 2.5 18.5 25.5 0.5 3.5 18.5 25.5 0.5 3.5 16.0 23.0
43.0 1.5 2.5 22.0 28.0 0.5 3.5 22.0 28.0 0.5 3.5 19.0 25.0

If the pressure values are not within the specified limits, the reason for this must be determined. The basis of the considerations when troubleshooting is the measurement of the values for the air conditioning system’s suction pressure and high pressure using a manometer. Please bear in mind that in a depressurised condition (ambient pressure), the manometers should indicate “0”.

Note

The information listed on the following pages could be possible causes.
Under certain conditions, other causes of error could be present.
Symbol (V) – only for compressors with a suction pressure regulator
Symbol (F) – only for compressors with a fixed displacement

Error

Possible cause

Low pressure too high
Example of using the diagnosis sheet

High pressure normal (l)
or too low (s)

  • The suction and pressure lines on the compressor are reversed (see Worksheet 6)
  • The compressor magnetic coupling slips or does not engage (see Worksheet 5)
  • The expansion valve is blocked in the open position.
    If the air conditioner is equipped with a compressor with a suction pressure regulator, small but rapid changes in pressure occur on the low pressure side (see Worksheet 3).
  • (V) The compressor’s suction pressure valve is defective or the factory setting is not suitable (see Worksheet 4)
  • The compressor is damaged (see Worksheet 9)

Low pressure too low
Example of using the diagnosis sheet

High pressure high (H)
or normal (l)

  • (F) The thermostat is defective (see Worksheet 8)
  • (F) The expansion valve is closed, i.e. blocked or clogged (see Worksheet 3)
  • The drying filter is saturated with moisture (see Worksheet 2)
  • (V) The compressor’s suction valve is blocked for the largest transport volume (see Worksheet 4)
  • (F) Stoppage in the refrigerant line between the filter and the expansion valve (see Worksheet 7)

Low pressure normal (l)
or too low (s)

Example of using the diagnosis sheet

High pressure normal

Low pressure high (H)
or normal (l)

Example of using the diagnosis sheet

High pressure too high

  • Possible normal operating pressure at high ambient temperature (> 43°C)
  • Excessive refrigerant filling (30-35% more than the prescribed amount, see Worksheet 2)
  • Impurities in the condenser
  • (V) Defective suction pressure regulator on the compressor (see Worksheet 2)
  • Stoppage on the high pressure side between the compressor, condenser and filter.
    Important – the stoppage can only be in the area around the service connection for high pressure,
    not on the low pressure side.

Low pressure normal (l)
or too low (s)

Example of using the diagnosis sheet

High pressure too low

  • Possible normal operating pressure at low ambient temperatures (> 5°C)
  • Possible normal operating pressure at low ambient temperatures
  • Low refrigerant volume, 70-75% below normal amount (see Worksheet 2)
  • (V) The expansion valve is closed (blocked) or clogged (see Worksheet 3)
  • (V) Stoppage on the low or high pressure side between the filter and evaporator (see Worksheet 7)
  • Stoppage between the compressor and condenser or the condenser and filter, however on the high pressure side (see Worksheet 7)

Low pressure and high pressure
manometers show the same value

Example of using the diagnosis sheet

  • Defective compressor (see Worksheet 9)
  • One possible cause of error is improper alignment of the pulleys (see installation instructions), the drive belt slips
  • The compressor magnetic coupling slips or is defective (see Worksheet 5)
  • Defective compressor (see Worksheet 9)
  • (V) Defective suction pressure regulator on the compressor (see Worksheet 4)

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