Here are two types of tasks mechanics usually do when carrying out car air con servicing.
They'll do a full inspection of the air conditioning system
As part of this servicing process, the mechanic will do a full inspection of the vehicle's entire air conditioning system. For example, they'll check the pressure of the system's refrigerant, using a specialist pressure gauge, to ensure its pressure level is acceptable. If the car owner has expressed concern about a potential refrigerant leak, the mechanic may also use leak-detecting equipment to see if this fluid is leaking.
They'll also examine the condition of the system's compressor, to see if it's showing signs of wear and tear. Additionally, they'll switch on the system and listen for unusual noises. If for example, they can hear a whirring noise, this could indicate that the blower motor is in need of repair. If they can detect a clicking sound, this might suggest that the system's blend door actuator is not functioning as it should. If they notice that the ventilation fans are excessively noisy, this might indicate that there is some debris stuck in the system that needs to be removed; in this situation, they might visually inspect the cabin air filter, the evaporator and the blower fan, as these are the areas where debris can often create obstructions.
They'll do a vacuum evacuation
During an air con servicing appointment, a mechanic will also sometimes carry out a vacuum evacuation; this process is designed to extract moisture and air from within the system before fresh refrigerant is added to it. They may do this if the servicing inspection results in them finding a refrigerant leak or if they have had to replace a part such as the condenser or compressor.
A vacuum evacuation can prevent the new refrigerant from being contaminated. This, in turn, ensures that the new refrigerant's role in maximising the system's cooling capacity is not affected by contaminants. To carry out this process, the mechanic will use a specialist vacuum pump to draw out air, moisture and debris from the system. Whilst doing this, they'll monitor the pressure levels with a pressure gauge and will finish the process when the pressure levels drop to an appropriate level (this is because low air pressure indicates that most of the air and moisture have been successfully eliminated from the system). They'll then add the new refrigerant to the decontaminated system.