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Checking heat output - vehicles with automatically controlled air conditioner > < Heat output of air conditioner

A1

Checking heat output - vehicles with manually controlled air conditioner
Checking heat output - vehicles with manually controlled air conditioner
Special tools and workshop equipment required
t  Vehicle diagnostic tester
t  Commercially available thermometer (for temperature measurement; if applicable use thermometer with 2 probes for simultaneous measurement of temperature e.g. on right and left)
Test requirements
l  Coolant circuit bled in specified manner → Rep. gr.19
l  All air ducts, covers and seals OK and properly installed
l  Air flow through dust and pollen filter not impeded by contamination; checking → Chapter „Removing and installing dust and pollen filter“
l  Vehicle not exposed to sunlight
l  Engine warm
l  Event recorder of operating unit, air conditioning system control unit -J301- interrogated and erased, basic setting performed in „Guided fault-finding“ function → Vehicle diagnostic tester
Checking
–  Close the front lid, doors, windows and sun roof.
–  Open all dash panel vents.
   
–  Start the engine and make the following settings on the operating unit:
l  Set the rotary temperature control -1- to the „Cold“ stop.
l  Air conditioner compressor on - lamp in AC button -4- lights.
–  Operate the air conditioner (with the engine running) for several minutes at maximum cooling output.
–  Set the rotary air distribution control -3- to „Dash panel vents“.
–  Set the rotary fresh air blower control -2- to speed „4“.
–  Use a thermometer to measure the temperature of the air emerging from the left and right dash panel vents.
l  Compare the measured values to the measured value displayed (for the evaporator output temperature sender -G263-). The values measured must not be lower and after 5 minutes not more than 3 °C higher than the value of -G263-.
Specifications:
l  Temperature max. 12 °C (depending on ambient temperature), difference between measured values less than 3 °C.
–  Set the highest possible temperature (rotary temperature switch on „Warm“ stop).
–  Use a thermometer to measure the temperature of the air emerging from the left and right dash panel vents.
Specifications:
l  Temperature increases (at engine temperature of approx. 90 °C) to greater than 45 °C, difference between left and right side less than 8 °C.
  Note
At ambient temperatures below 10 °C, the temperature of the air emerging from the left and right dash panel vents will not always be higher than 45 °C in the selected setting „maximum fresh air blower speed, engine idling“. The engine speed is therefore to be increased to 1500 rpm when performing this test at low ambient temperatures.
–  Set the lowest possible temperature (rotary temperature switch on „Cold“ stop).
–  Use a thermometer to measure the temperature of the air emerging from the left and right dash panel vents.
Specifications:
l  Temperature drops to less than 12 °C within 5 minutes (depending on ambient temperature).
Check the following if the readout does not match the specifications:
If the air emerging from the vents is too warm in the „Cold“ setting:
–  Air conditioner cooling output → Chapter
If the air emerging from the vents is too cold in the „Warm“ setting:
–  Coolant circuit bleeding → Rep. gr.19.
–  Incorporation of the heating system heat exchanger into the coolant circuit → Rep. gr.19.
–  The flexible temperature adjustment shaft and actuation of the temperature flap (the flap must reach both end stops) → Chapter.
–  The foam seal at the heating system heat exchanger → Chapter.
–  Operation of the temperature flaps in the air distribution housing → Chapter „Removing and installing air distribution housing“.
–  Check the thermostat (the engine coolant may not become properly warm if the thermostat is defective) → Rep. gr.19.
–  Check operation of the temperature flaps in the air distribution housing → Chapter „Removing and installing air distribution housing“.
If no fault is found:
–  Increase the engine speed to approx. 1500 rpm and check the temperature again.
If the heat output is then OK:
–  Check the thermostat (the engine coolant may not become properly warm if the thermostat is defective) → Rep. gr.19.
–  Check the coolant pump → Rep. gr.19.
  A87-10864

Checking heat output - vehicles with automatically controlled air conditioner > < Heat output of air conditioner