[Andy4639]

Originally Posted by davepl

Thanks. Dumb question, but where would a guy that doesn't have specialized AC tools hook up to the system in order to pull a vacuum?

There should be shrader valves on the lines with blue caps. These are low pressure side fitting to hook to.
No specialized tools needed for this.





(1) Heating System

Heat is a byproduct of the engine's combustion process. The coolant, or anti-freeze in your car’s radiator absorbs the heat. The coolant is then circulated through the heater core before returning to the radiator. The heating system also includes a series of air ducts, a blower motor and fan, and temperature and duct controls, which select the desired temperature and direct the flow of warm air.

(2) Compressor
This is a pump that pressurizes and circulates the refrigerant through the system. The compressor builds the pressure of the refrigerant up, close to 250 pounds per square inch (psi).

(3) Condenser
The condenser is located in front of the vehicle's radiator. As the refrigerant flows through the condenser, it gives off heat and converts from gas to liquid. This is where heat from the cabin is transferred to the ambient, or outside air via the refrigerant.

(4) Receiver/Drier or Accumulator
This is where clean, dry refrigerant is stored as it circulates through the system. The receiver/drier has a filter and a desiccant, similar to that in your pill bottle, to remove moisture from the refrigerant. It is a good idea to change this filter anytime this sealed system is opened for repair.

(5) Orifice Tube or Expansion Valve
This is a metering device that controls the flow of refrigerant through the system.

(6) Evaporator Core
The evaporator is like a 'tiny radiator' with refrigerant flowing through it, instead of anti-freeze. Warm air from the cabin is drawn into the evaporator box by the blower motor and pulled over the cooling fins of the evaporator. Heat from the cabin air is absorbed through the cooling fins and into the refrigerant. Moisture in the air condenses on the evaporator fins, drips down into the evaporator box, then runs out a small drain under the vehicle. The cooled/dehumidified air is then circulated back into the cabin.

How the a/c system works.

Air conditioners and refrigerators work the same way. Instead of cooling just the small, insulated space inside of a refrigerator, an air conditioner can cool a whole car or house.

Air conditioners use chemicals that easily convert from a gas to a liquid and back again. This chemical is used to transfer heat from the air inside of the car to the outside air.

The system has three main parts. The compressor, the condenser and the evaporator. The compressor mounted on the engine and is powered by the engine via a belt. The condenser is located at the front of the car to take advantage of air coming toward the moving vehicle. The evaporator is located inside the cabin of the car under the dash near the firewall.

The working fluid arrives at the compressor as a cool, low-pressure gas. The compressor squeezes the fluid. This packs the molecule of the fluid closer together. The closer the molecules are together, the higher its energy and its temperature.

The working fluid leaves the compressor as a hot, high pressure gas and flows into the condenser. If you looked at the condenser, look for the part that has metal fins all around. The fins act just like the radiator in the car and helps the heat go away, or dissipate, more quickly.

When the working fluid leaves the condenser, its temperature is much cooler and it has changed from a gas to a liquid under high pressure. The liquid goes into the evaporator through a very tiny, narrow hole- the expansion valve, or orifice tube. On the other side, the liquid's pressure drops. When it does, it begins to evaporate into a gas.

As the liquid changes to gas and evaporates, it extracts heat from the air around it. The heat in the air is needed to separate the molecules of the fluid from a liquid to a gas. The metal fins on the evaporator help in the exchange of thermal energy with the surrounding air.

By the time the working fluid leaves the evaporator, it is a cool, low pressure gas. It then returns to the compressor to begin its trip all over again.

Connected to the evaporator is a fan- the blower motor, that circulates the air throughout the car and over the evaporator fins. Hot air is lighter than cold air, so the hot air in the car rises toward the roof of the car.

There is a vent there where air is sucked into the air conditioner and goes down ducts. The hot air is used to cool the gas in the evaporator. As the heat is removed from the air, the air is cooled. It is then blown into the car through the air ducts.

This continues over and over and over until the vehicle reaches the desired temperature. The thermostat senses that the temperature reached the right setting and turns off power to the a/c compressor clutch. This stops the compressor from circulating the refrigerant. As the cabin warms up, the thermostat returns power to the compressor clutch so the compressor begins to turn, again circulating the refrigerant through the system.

Air conditioning tips:

* For maximum cooling: Park your car in the shade during the day and leave your windows open slightly to let cooler air into your car. When your car is parked in the sun during the summer, temperatures inside the cabin can reach 200º Fahrenheit. By parking in the shade your car will not have to cool the air in the passenger compartment (cabin) from such a high temperature to a temperature that is comfortable to you.

* For maximum cooling: When starting out, if the car has been sitting in the sun and is very hot inside open all windows with the air conditioner on and wait until the air inside is a little on the cool the side before closing the windows. By doing this you are not having to rely on the air conditioner alone to bring the temperature down.

* For maximum cooling: Set the system to "re-circulate." This shuts off hot air from the outside, so your a/c is cooling the cooler air from inside the cabin as the air conditioner runs. The system will cool much more efficiently than when set to other settings which draw hot and humid air inside the cabin. This will bring the temperature down faster and keeps out unpleasant air for example, when the car ahead of you that has smoke coming out the tailpipe.

* For maximum cooling: Use the lowest possible fan speed setting. This slows the movement of cabin air going through the evaporator. The slower the air moves through the evaporator, the more time the refrigerant has to "soak" the head out of the air and, the cooler the air coming out of your a/c vents.

* The cooler your car is inside when you turn on the a/c the quicker the heat transfer is achieved to the desired temperature. To keep it cooler when parked, park in a parking garage, use a windshield sun-block and keep your windows cracked open slightly to allow hot air to escape.

* During the winter run your air conditioner 5 or 10 minutes once a month to circulate the oil through the system. Windshield defoggers in many modern cars activate the a/c compressor to dry the air before it is warmed by the heater core and routed to the windshield. You probably won't have to worry about turning on your a/c in the winter if your defroster automatically turns on the a/c system in your car.

* Keep leaves out from under the hood, and under the wipers where the fresh air intake vents are. The leaves can block air flow and get into the evaporator, where they will rot, mulching up and blocking the evaporator drain. This causes condensation to build up and overflow onto the front floor boards of the car. Poor condensation flow over long periods can cause the evaporator to corrode and eventually leak, allowing the refrigerant to escape. To correct either of these problems the evaporator box may have to be removed. This is a very expensive job.