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How Auto Air Conditioning Works:

Air conditioning is the process by which air is cooled and dehumidified. The air conditioning in your car, your home and your office all work the same way. Even your refrigerator is, in effect, an air conditioner.
Air conditioning systems operate on the principles of evaporation and condensation. The principles of evaporation and condensation are utilised in your car's A/C system by a series of components that are connected by tubing and hoses. There are six basic components:
  • Compressor
  • Condenser
  • Receiver-drier
  • Thermostatic expansion valve
  • Evaporator
  • Refrigerant
Refrigerant is the life blood of the A/C system, a liquid capable of vaporising at a low temperature. Due to the harmful chlorofluorocarbon (CFC) in the formerly used R-12 refrigerant, all vehicles built after 1996 use R-134A, a more environmentally friendly refrigerant. The latest refrigerant R1234yf is currently coming on-stream and now being used in vehicles in Australia and New Zealand. Mobile workshop vehicle air conditioning service units are now available for those vehicle workshops servicing auto A/C units. There are also hybrid units available incorporating both R134A and R1234yf. 
Here's how an air conditioning system and its components work:
  1. The compressor is the power unit of the A/C system. It is powered by a drive belt connected to the engine's crankshaft. When the A/C system is turned on, the compressor pumps out refrigerant vapour under high pressure and high heat to the condenser.
  2. The condenser is a device used to change the high-pressure refrigerant vapour to a liquid. It is mounted ahead of the engine's radiator, and it looks very similar to a radiator with its parallel tubing and tiny cooling fins. If you look through the grille of a car and see what you think is a radiator, it is most likely the condenser. As the car moves, air flowing through the condenser removes heat from the refrigerant, changing it to a liquid state.
  3. Refrigerant moves to the receiver-drier. This is the storage tank for the liquid refrigerant. It also removes moisture from the refrigerant. Moisture in the system can freeze and then act similarly to cholesterol in the human blood stream, causing blockage.
  4. As the compressor continues to pressurise the system, liquid refrigerant under high pressure is circulated from the receiver-drier to the thermostatic expansion valve. The valve removes pressure from the liquid refrigerant so that it can expand and become refrigerant vapour in the evaporator.
  5. The evaporator is very similar to the condenser. It consists of tubes and fins and is usually mounted inside the passenger compartment. As the cold low-pressure refrigerant is released into the evaporator, it vaporises and absorbs heat from the air in the passenger compartment. As the heat is absorbed, cool air will be available for the occupants of the vehicle. A blower fan inside the passenger compartment helps to distribute the cooler air.
  6. The heat-laden, low-pressure refrigerant vapour is then drawn into the compressor to start another refrigeration cycle.
Almost every vehicle's A/C system works this way, however certain vehicles may vary by the exact type of components they have.

Basic Auto Air Troubleshooting

It is rare to have many problems with modern auto air conditioning. Most problems that do arise stem from one of two things: no cool air or insufficient cool air. If you own an older car and its A/C system doesn't seem to be working properly, here are some general troubleshooting tips:
No cool air – possible problems:
  • Loose or broken drive belt
  • Inoperative compressor or slipping compressor clutch
  • Defective expansion valve
  • Clogged expansion valve, receiver-drier or liquid refrigerant line
  • Blown fuse
  • Leaking component: any of the parts listed above or one of the A/C lines, hoses or seals

Insufficient cool air - possible problems
  • Low refrigerant charge
  • Loose drive belt
  • Slipping compressor clutch
  • Clogged condenser
  • Clogged evaporator
  • Slow leak in system
  • Partially clogged filter or expansion valve
Most A/C repairs are best left to an expert technician. Recharging the refrigerant in particular requires special equipment. Contact Coolvac’s team of experts to discuss your issues.

Recovering Gas from a Vehicle

When recovering gas from a vehicle, ensure it is done at a moderate pace. Most automotive A/C systems take on average 100-150ml of oil. This oil is circulated with the gas around the system and at any one time. If too much oil is removed from a system the compressor will fail prematurely. Most automotive recovery machines have an integrated oil separator. This separator is only so efficient at extracting the oil from recovered gas. If gas is recovered too fast, users run the risk of the oil being pumped into the reclaim bottle and thereby are unaware of how much oil the system is short of.

As a general rule, recover from the low side of the vehicle A/C system first. Limit the speed of recovery by throttling the valve on the recovery unit. When the majority of the gas has been recovered, the high side may be used to recover. This ensures no liquid refrigerant carries excessive amounts of oil back into the recovery unit.

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