When measuring the actual temperature drop of the air through the air conditioning system with a thermometer, the fan should be on its lowest setting, because the slower any given mass of air passes across the condenser, the greater the cooling effect. The objective of this procedure is to show you how to check the condition of air conditioning system components.
Part 1. Preparation and safety
- Check the condition of air conditioning system components.
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:
- Work clothing - such as coveralls and steel-capped footwear
- Eye protection - such as safety glasses and face masks
- Ear protection - such as earmuffs and earplugs
- Hand protection - such as rubber gloves and barrier cream
- Respiratory equipment - such as face masks and valved respirators
If you are not certain what is appropriate or required, ask your supervisor.
- Always make sure that you wear the appropriate personal protection equipment before starting the job. It is very easy to hurt yourself even when the most exhaustive protection measures are taken.
- Always ensure that your work area/environment is as safe as you can make it. Do not use damaged, broken or worn out workshop equipment.
- Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.
Points to note
- When checking the relative air temperature, the higher the ambient temperature the greater the expected drop in temperature of the air being discharged by the air conditioning system. When the normal temperature of the air is fairly cool anyway, the air conditioning effect will be relatively lower.
- Personal perception of coolness is relative. On a hot day, an air conditioning fan on full blast may feel cooler than a fan on a lower setting, because of the cooling effect of the evaporation of perspiration on your skin. But when measuring the actual temperature drop of the air through the air conditioning system with a thermometer, the fan should be on its lowest setting, because the slower any given mass of air passes across the condenser, the greater the cooling effect.
- If you suspect a leak in a hose connection, there are a number of ways that the leak may be detected. Different manufacturers recommend different procedures. Refer to the shop manual for the vehicle you are working on for the correct procedure.
- Some earlier systems have a sight glass somewhere in the high-pressure side of the system. This gives you some visual information about the state of the refrigerant. In normal operation, the sight glass is clear.
- When the clutch engages, you should see a short burst of bubbles in the sight glass soon afterwards. If the bubbles continue, this can indicate a less than fully charged system. If the system is badly discharged, there will be no bubbles at all. If the refrigerant appears cloudy, this indicates moisture or some other contamination is in the system.
Part 2: Step-by-step instruction
- Check drive belts
Check the tension and condition of the belt around the compressor pulley. An air conditioning compressor uses quite a lot of power so a loose belt, or one glazed from slippage in the past, may not be driving the compressor properly,
- Check condition of condenser
Check the condenser to make sure that it is not clogged with mud or leaves which will prevent it from radiating to the outside the heat collected from the inside of the vehicle. The fins on the condenser can be cleaned with water and a stiff brush if necessary
- Check condition of hoses
Check that the flexible hoses to the various components of the air conditioning system are not cracked or soft or brittle and that they are connected securely with no obvious signs of leakage or corrosion around the connections.
- Check the security of rigid lines
Some of the hoses may be metal pipes. Check that these rigid lines are securely fixed in their routing positions and also look for signs of leakage at their connections.
- Check for oil stains
Some lubricating oil circulates with the refrigerant in an air conditioning system, so look for wet stains around all the hose connections, as well as around the gaskets on the compressor, as these may also indicate refrigerant leakage.
- Run system and check sight glass if fitted
Start the engine and then switch on the air conditioner. You should hear a firm click as the compressor clutch engages. Set the blower fan to high and check whether the air coming out of the vents inside the vehicle feels cool. Then switch the fan to its lowest setting and use a stem/dial thermometer to compare the ambient temperature. With the cooler air coming out of the air conditioning system. The difference should generally be around 20°F or 11°C although this will vary with different outside temperatures. Let the engine run at around 1500 rpm with the air conditioner on for 5-10 minutes. Then feel the hoses on each side of the compressor. The high side or outlet hose of the compressor should feel significantly hotter, than the low side or inlet hose.