A/C Cooling Output, Testing Requirements
A/C Cooling Output, Testing Requirements
Only for vehicles with mechanically driven A/C compressor and not for vehicles with a high voltage electrical system (hybrid vehicles)
• Ambient temperature greater than 15 °C (59 °F).
• Radiator and condenser are clean (if necessary clean)
• The ribbed belt for A/C compressor drive is OK and correctly tensioned and the belt pulley actually drives the A/C compressor (on vehicles with a 4- or 6-cylinder engine). Refer to => [ A/C Compressor Belt Pulley ] A/C Compressor Belt Pulley.
• The A/C compressor ribbed belt is OK and is tensioned correctly, the Climatronic control module (J255) is activating the A/C clutch (N25) and the belt pulley is driving the A/C compressor (only on certain vehicles with an A/C compressor with a magnetic clutch, introduction from MY 12, for example, on vehicles with a certain 4 cylinder engines). Refer to => [ Belt Pulley with A/C Clutch (N25) Overview ] Belt Pulley With A/C Clutch (N25) Overview and the Vehicle diagnostic tester in "Guided Fault Finding".
• The A/C compressor drive unit is mounted correctly and the A/C compressor is actually driven (on 8 cylinder vehicles), refer to => [ A/C Compressor Drive Unit Overview ] A/C Compressor Drive Unit Overview.
• All air ducts, covers and seals OK and properly installed
• Air flow through dust and pollen filter not obstructed by dirt. Refer to => [ Dust and Pollen Filter ] Service and Repair.
• Air intake apparatus (in fresh air and recirculating air mode) is not impaired by soiling or components installed as retrofit.
• Vehicle not exposed to sunlight
• The engine is warm (the coolant temperature is higher than 80 °C (176 °F)).
• Climatronic control module DTC memory was checked and erased, basic setting was performed and the Climatronic control module coding was checked using the Vehicle diagnostic tester in "Guided Fault Finding"
• The Climatronic control module adaptation was checked using the Vehicle diagnostic tester in "Guided Fault Finding".
• All instrument panel vents open
• The hood is closed.
• The engine is running.
Set the "Basis" Climatronic control module display and control head as follows:
• "Auto" operating mode (indicator light on the AUTO button lights up).
• Temperature preselect "cold" (display"LO" in the MMI display).
• The A/C compressor is on (the indicator lamp on the AC button comes on).
• Preselect for the fresh air blower "maximum speed" (in the Multi Media Interface display, level "10" or greater).
The Climatronic control module of "Comfort" version is set as follows:
• "Auto" mode (the indicator lamp in both AUTO buttons illuminate).
• Temperature preselect "cold" for the driver's and passenger's side (display"LO" for the driver's and passenger's side in the A/C Control Head display and in the Multi Media Interface display).
• The A/C compressor is on (the indicator lamp on the AC button comes on).
• Preselect for the fresh air blower "maximum speed" (display in the A/C Control Head and in the Multi Media Interface display, level "10" or greater).
• The indicator lamp in the AUTO button(s) goes out when the fresh air blower speed is changed manually.
• The maximum possible fresh air blower speed depends on several conditions (coolant temperature, vehicle voltage, etc.)
- On vehicles equipped with the "Comfort" A/C system, the Rear Temperature Selection Potentiometer (G538) is set to "cold" (installed in the rear center console vent).
- On vehicles equipped with the "Comfort" A/C system, the vent in the rear center console is open.
Functions with engine running
- The coolant fans ( coolant fan (V7) and coolant fan 2 (V177) ) run (activation and speed depend on pressure in coolant circuit and engine temperature).
• Depending on the version of the Climatronic control module, the coolant fans ( coolant fan (V7) and coolant fan 2 (V177) ) are only switched on at a certain pressure in the coolant circuit (currently, at a pressure of approximately 9 bar (130.5 psi)). The coolant fan(s) control is displayed in the measured values block. Refer to the Vehicle diagnostic tester in "Guided Fault Finding".
- The Fresh Air Blower (V2) runs with maximum speed ("10" or greater).
• The maximum possible fresh air blower speed depends on several conditions (coolant temperature, vehicle voltage, etc.)
- The air conditioner goes in recirculation mode (approximately 1 minute after starting the engine, the back pressure/fresh air door is closed and the recirculation door is opened, Fresh Air Blower. extracts the air from passenger compartment below instrument panel / behind the glove compartment).
• If one of these requirements is not filled, check the DTC memory, perform output diagnostic test mode and read the measured values block using the Vehicle diagnostic tester in "Guided Fault Finding".