1 - Principles of operation of the automotive air conditioning.2 - Why maintain his air conditioning?
3 - Maintenance of automotive air conditioning.
4 - My air conditioning does work properly?
Principles of operation of the automotive air conditioning
1 - Compressor
It serves to ensure a refrigerant flow in the refrigerant circuit (it compresses the low-pressure gas in the high-pressure gas).
The compressor mechanism is lubricated by a special oil.
2 - The regulator.
This reduces the pressure and controls the flow of the refrigerant in the evaporator so that there is always a liquid-vapor mixture from the beginning to the end of the evaporator, thereby enabling to absorb the fluid heat from the air and to vaporize completely there is, therefore, production of cold.
3 - The condenser.
It serves to cool the fluid so that it turns liquid (passage of high-pressure gas in the high-pressure liquid). The outside air passing through the condenser allows this change of state, helped by a fan
4 - The dryer or desiccant cartridge
Its role is threefold:
- Ensure the smooth buffer reserve, allowing for continuous feed
the regulator in the high pressure liquid fluid.
- Filtering the fluid impurities.
- Retain the moisture in the circuit (through silica salts).
5 - The evaporator.
Its function is to cool and dehumidify the air eventually entering the vehicle cabin.
The outside ambient air which enters the passenger compartment through the evaporator fins loses some of its heat, which will allow the fluid to vaporize. The air is cooled while the fluid exits the evaporator in gaseous state
The air, passing on the cooled blades, loses its moisture (if the external humidity is high) that will turn into the water by condensation. This air is thereby dehumidified and partly dust (dust adhere to the water film forming on the evaporator).
Note: It is normal to find water flowing under the vehicle when the air conditioning system is operating. (eg., Washington, reduced humidity is 95-45% => 3 l of water withdrawn per hour).
6 - The pressure switch.
It controls the clutch control ( the compressor switching on), the group
fan motor and ensures high safety and low system pressure.
Placed on the dehydrator reservoir, it provides three electric switching functions for
Security of the refrigeration system, hence the name "3-level switch".
The switch allows you to:
- Turn off the compressor if the pressure of the refrigerant gas is less than about 1.2 bars (level 0), or higher than 32 bars (level 2)
- Engaging the second speed of the engine cooling fan if the gas pressure exceeds about 16 bars (level
7 - The frost thermostat.
The frost thermostat or evaporator probe is in contact with the evaporator and allows the compressor stop if its surface temperature is too low to avoid ice making the exchanger.
8 - The pipes and fittings.
They allow to convey the refrigerant to the various organs of the plant while being resistant to the pressure and temperature of that fluid, as well as external chemical agents (engine oil, battery acid, winter salting products of the floor, etc.).
Two types of pipes are used:
1- Hose, allowing them easy passage in tight places and filter the vibrations and movements of the motor in relation to the bodywork.
- Rigid piping, in cadmium plated steel or aluminum for the R 134a, to minimize bulk by smaller radii of curvature than the hose.
2 - Why maintain his air conditioning?
It is often said "as long as it works, do not touch ©". But at the same time, it just has to see the number of people that have a problem with their air conditioning. So what about maintenance?
First you must know that the air conditioning circuit contains two components:
- A gas, currently R134a (1,1,1,2-tetrafluoroethane or C2H2F4). It does not attack the ozone layer (unlike the old R12) but has itself a greenhouse.
- A special oil for the compressor lubricant
1 - The loss of gas
The system is supposed to be sealed.
The molecule of R 134a, is smaller than that of CFC 12, tends to pass through the sealing material. To overcome this drawback a second nylon-based layer has been inserted on the flexible pipe.
To try to limit the risk of a loss of gas conditioning must turn at least every 15 days (especially in winter, at least for 1/2 hour) to improve the flow of oil (pending with the fluid) to lubricate joints.
2 - The water problem.
oils are highly hygroscopic, ie they have a strong tendency to absorb moisture from the air. The dryer holds this moisture, but its capacity is limited: maximum 60 drops of water is 3 g water!
But the circuit being intended to be sealed and pressurized, which can come from water?
- A degree of inadequate or insufficient vacuum before charging the refrigerant.
Why is water so dangerous?
Schematically: - oil + water = acid formation (HF). - Acids + = metal sludge. - Sludge = + obstruction of poor lubrication circuit.
Furthermore, the water not being soluble in the fluid, the excess water will turn into ice which obstruction of the circuit, especially on the pressure.
3 - Maintain his conditioning.
3.1 - The cabin filter or pollen filter.
Its role is to ensure effective filtration of outdoor air, thus protecting the occupants of various inconveniences: pollen, dust, soot ...
The problem in the case of non-replacement is that it clogs (too much dirt before the filter).
Consequences:
- It does not leave enough air to pass:
there is no longer enough air so heat absorbing cooling fluid evaporates and evil can happen
liquid rather than the steam compressor and thereby destroy the compressor.
Consequence: the air coming out of the vents will not be colder.
- All "dirt" accumulated before the filter creates the opposite effect to that intended.
The fresh outside air passes first in this nest of germs and bacteria which
finishes inevitably pass into the passenger compartment and thus into our lungs ...
Conclusion: It is imperative to change the filter at least once a year and will not hesitate to change it as often as necessary (every 15.000km).
3.2 - Disinfection.
The air conditioner is indeed a perfect mold factory. We have seen that share its operation, the evaporator will "create" water, dehumidifying the air outside. When stopping the air conditioning, the lower part of the evaporator, still very humid, going from cold to room temperature. We are in the presence of a dark and damp area warms, the ideal condition for bacteria and bad odors develop. When restarting the air, some of these bacteria and odors are driven with the air stream and contaminate the entire ventilation system and cockpit.
Conclusion: -It is necessary to disinfect the circuit once a year. You must obtain a bactericide and fungicide: air conditioning stopped, remove the filter, put the maximum ventilation and spray the product by the outer gate and leave.
3.3 - My air conditioning does work properly?
Here are the acceptable temperature data at the output of the central vents depending on the ambient temperature outside the vehicle at the air intake grille, the air conditioning must be put in cold medium and max fan speed can raise temperatures after 10 minutes of running air conditioning.
These values are used to assess whether your air conditioner is a cooling load problem. Although this method is imprecise, it has the merit of giving an idea of the condition of the air conditioning in your car.
Temperature amb ext / acceptable temperature at the exit of aerators, set engine speed (stopped) at 1800 rev / min:
3.4 - Preventive cleaning.
Should be cleaned once a year your condenser if it is very dirty with a (WARNING well protected with a tarp all engine electrical appliances dismantle the fans if needed to properly access the condenser) for routine maintenance ( not too dirty condenser) blow with an air compressor or made water trickle over paying attention to water splashes. This simple cleaning allows a good heat exchange in the condenser and consequently to have a normal pressure in the system reducing the risk of compressor breaking.
3.5 - Recharging
This is the process of handing the gas but also oil the function, remember, is essential as it allows, among other things, to lubricate the compressor. During a refill for leaks is also checked.
Conclusion: If the air conditioning system has a leak will require a fluid charging as this leakage causes poor performance of the air conditioning.
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