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Continuation Of Test: Pressure In Refrigerant Circuit Increases

-- Open hood.-- Repeat cooling performance test COOLING OUTPUT, CHECKING .
  • Do(es) Coolant Fan(s) -V7- run during cooling performance test (speed depends on coolant temperature and pressure in refrigerant circuit, speed is determined by Engine Control Module (ECM))?
↓ Yes ↓ ↓ No ↓
-- Read the pressure in the refrigerant circuit and the radiator fan control using Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".
  • Is the coolant fan running at a faster speed as the refrigerant circuit pressure increases?
 -- Check the coolant fan activation using "output diagnostic test mode" of Vehicle Diagnosis, Testing and Information System VAS 5051. -- Correct the coolant fan activation.
↓ Yes ↓ ↓ No ↓ -- Repeat cooling performance test COOLING OUTPUT, CHECKING .
-- Bring vehicle to a workshop that has the necessary tools and in which the work can be performed accordingly by qualified personnel RADIATOR AND COOLANT FAN OVERVIEW and refer to A/C PRESSURE SWITCH -F129- and refer to A/C REFRIGERANT HIGH PRESSURE SWITCH -F23- . Bring the problems determined to the attention of the workshop. -- Check the coolant fan activation, with "output diagnostic test mode" of Vehicle Diagnosis, Testing and Information System VAS 5051.-- Correct the coolant fan activation.
NOTE:
  • The pressure in the refrigerant circuit depends on several factors. However, in general, the pressure should not exceed 20 bar at an ambient temperature of 20 to 25 °C. Pressures up to 31 bar may occur due to extremely high performance under severe conditions (such as in southern countries with a hot climate, "stop and go" traffic and high humidity).
  • At temperatures below 25° C, the pressure in the refrigerant circuit generally does not rise above 16 bar (the coolant fans run and cool the condensers down).
  • The Climatronic control module calculates the refrigerant circuit pressure via the duty cycle.
  • If the duty cycle is less than 10% (matches approximately 1.2 bar absolute pressure) or greater than 78% (matches approximately 32 bar absolute pressure) the Climatronic control module does not switch on the A/C compressor (the A/C compressor regulator valve is not controlled). The A/C compressor is only switched on again after duty cycle has become greater than 12% (corresponds to 1.8 bar absolute pressure) or less than 48% (corresponds to 16 bar absolute pressure).
  • If the pressure in the refrigerant circuit or the engine coolant temperature is too high, the Climatronic control module regulates the A/C compressor performance (to avoid sudden compressor cut-off): As soon as the refrigerant circuit pressure goes above 30 bar (absolute pressure). The full A/C compressor output will be released once after the pressure is less than 27 bar or when the coolant temperature goes above 115 °C (the A/C compressor switches off completely at 118 °C).
  • If the pressure in the refrigerant circuit was greater than 32 bar (duty cycle greater than 78%) the A/C compressor is switched on again by Climatronic control module, if pressure drops below 29 bar (duty cycle is less than 74%).
  • Additional information regarding the pressure in the refrigerant circuit can be found in Vehicle Diagnosis, Testing and Information System VAS 5051 under "Guided Fault Finding".
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