Refrigeration System
Refrigerant R-134aCaution: Avoid breathing the A/C Refrigerant 134a (R-134a) and the lubricant vapor or the mist. Exposure may irritate the eyes, nose, and throat. Work in a well ventilated area. In order to remove R-134a from the A/C system, use service equipment that is certified to meet the requirements of SAE J 2210 (R-134a recycling equipment). If an accidental system discharge occurs, ventilate the work area before continuing service. Additional health and safety information may be obtained from the refrigerant and lubricant manufacturers.
Refrigerant performs the following functions in the air conditioning system:
- Absorbs heat
- Carries heat
- Releases heat
These vehicles use Refrigerant-134a (R-134a). Refrigerant-134a is a nontoxic, nonflammable, clear, colorless liquefied gas.
Blower Motor
The blower consists of the following components:
- A permanent magnet type motor
- A squirrel cage type fan
The blower operates at various speeds. The various speeds are determined by the resistance of the blower motor resistor which is controlled by the blower motor speed control.
Expansion (Orifice) Tube Description
The plastic expansion (orifice) tube, with its mesh screen and orifice, is located between the condenser outlet and evaporator inlet. It provides a restriction to the high-pressure liquid refrigerant in the liquid line, metering the flow of refrigerant to the evaporator as a low-pressure liquid. The expansion (orifice) tube and orifice are protected from contamination by filter screens on both inlet (1) and outlet (3) sides.
When system diagnostics indicate a restricted expansion (orifice) tube, it may not be necessary to replace the tube. Metal chips, flakes, or slivers found on the screen may be removed with compressed air and the expansion (orifice) tube may be reused if:
- The plastic frame is not broken.
- The brass expansion (orifice) tube is not damaged or plugged.
- The screen material is not torn.
- The screen is not plugged with fine gritty material.
Evaporator Description
The evaporator cools and dehumidifies air before the air enters the passenger compartment. The following events occur in the evaporator:
1. Low-pressure, low temperature liquid/vapor refrigerant enters the evaporator.
2. The refrigerant flows through the evaporator's tubing.
3. The refrigerant evaporates.
4. The refrigerant exits the evaporator as low-pressure, low temperature, mostly vapor refrigerant.
5. As the refrigerant evaporates, the refrigerant absorbs heat from the air flowing over the evaporator.
As the process of heat loss from the air to the evaporator core is taking place, any moisture (humidity) in the air condenses on the outside surface of the evaporator core and the moisture drains off as water.
Condenser Description
The condenser receives high pressure, high temperature refrigerant vapor from the A/C compressor. The condenser is made up of aluminum tubing and cooling fins which allow rapid heat transfer away from the high-pressure, high temperature refrigerant vapor. The cooling fins cause the high pressure, high temperature refrigerant vapor to condense into a high-pressure, medium temperature liquid.
Accumulator Description
The sealed accumulator is connected to the evaporator outlet pipe. The accumulator stores the refrigerant (vapor and liquid) and the oil from the evaporator. A desiccant at the accumulator bottom dries any moisture in the system. An oil bleed hole at the accumulator outlet pipe end provides the oil return path to the compressor. The accumulator is not serviceable and should only be replaced when leaking due to the following conditions:
- Perforation
- A damaged sealing area
- Damaged fastener threads
- Outside air has entered the system for extended periods of time
High Pressure Relief Valve Description
The compressor is equipped with a pressure relief valve which is placed in the system as a safety factor. Under certain conditions, the refrigerant on the discharge side may exceed the designed operating pressure. To prevent system damage, the valve is designed to open automatically at approximately 3036 kPa (455 to 525 psi). Correct any condition that causes this valve to open and replace any expelled refrigerant oil. Inspect the air conditioning refrigerant pressure sensor for proper calibration.