307D, 311D, 312D, 313D, 315D, 318D, 319D, 320D, 323D, 324D, 325D, 326D, 328D, 329D, 330D, 336D, 340D, 345D, 349D, 374D, 390D and M325D Excavators Air Conditioning and Heating General Information Caterpillar


General Information
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307D, 311D, 312D, 313D, 315D, 318D, 319D, 320D, 323D, 324D, 325D, 326D, 328D, 329D, 330D, 336D, 340D, 345D, 349D, 374D, 390D and M325D Excavators Air Conditioning and Heating [RENR7298]
1.1. Identifying The System
2.1. Glossary of Terms

The air conditioning system is a closed circuit that uses the refrigerant, which is under pressure, to cool the operator compartment.

The air conditioning unit is an expansion valve system. The five components of the expansion valve system are the compressor, the condenser coil, the receiver-dryer, the expansion valve and the evaporator coil.

Identifying The System

Examine the charging ports. If one port is smaller than the other port, the air conditioning system contains R-134a refrigerant.



Illustration 1g00291316
(1) Block fitting at compressor with R-134a charging ports

If the machine has R-134a charging ports, a tag should identify the type of compressor oil that is used. The tag can be located inside the cab. The tag may also be located near the compressor. The tag will also display the amount of refrigerant in the system.

If the machine was delivered from the factory with R-134a refrigerant, the tag will display PAG (Polyalkylene Glycol). PAG oil is the lubricant for the system.

Glossary of Terms

Ambient air - Outside air

Charge - The charge is a predetermined amount of refrigerant that is put into the air conditioning system by weight.

Compressor - The compressor is a component in the system that increases the pressure of the refrigerant in the system by pumping.

Condenser - The condenser is a component in the system that changes the refrigerant from gas to a liquid.

Contaminants - Dirt, water and air

Desiccant - The desiccant is part of the receiver or the accumulator that removes the moisture from the air conditioning system.

Detecting - Detecting is finding the source of the problem in the system.

Diaphragm - The diaphragm is a rubber-like material. The diaphragm divides the upper chamber and the lower chamber in the thermostatic expansion valve.

Discharge - The discharge is the removal of some of the refrigerant or the removal of all the refrigerant from the air conditioning system.

Discharge side - The discharge side is the outlet from the compressor to the condenser coil.

Evacuating - Evacuating is the removal of air and moisture from the air conditioning system.

Evaporation - Evaporation is the process of changing a liquid to a vapor.

Evaporator - The evaporator is the component in the air conditioning system that changes the refrigerant from a liquid to a gas by the addition of heat.

Expansion Valve - The expansion valve is a component in the air conditioning system that regulates the flow of liquid refrigerants into the evaporator.

Fluid - Fluid is a liquid or a gas.

Formation of Bubbles - Bubbles in the sight glass of the receiver-dryer implies that too little refrigerant remains.

Flush - To remove foreign material and oil from the system, you must flush the system with fluid that is approved. The fluid must be approved by the SAE standard and approved by the ISO standard.

Freeze - Freezing can cause a liquid to become a solid.

Gas - gas is a vapor which contains no liquid.

Graduated Container - A graduated container is a glass scale that is used to measure a fluid in ounces or milliliters.

Heat - Thermal energy

Identifier - The identifier is an instrument for testing the system. The identifier is used for determining the type of refrigerant in the system. The identifier is also used for determining the percent of air in the system.

In-line dryer - A component of the air conditioning system that removes contaminants (moisture) from the system

Latent heat - The quantity of heat needed to cause a change of state between liquid and gas of the refrigerant without changing the temperature of the refrigerant.

Latent heat of condensation - The quantity of heat that is released from a vapor as the vapor is changed into a liquid at a constant temperature.

Latent heat of evaporation - The quantity of heat that is absorbed by a liquid as the liquid is changed from liquid into a vapor at a constant temperature.

Leak detector - The leak detector is a device that is used to locate leaks in the air conditioning system.

Liquid line - The liquid line is the line that connects the condenser coil, the receiver-dryer and the expansion valve together in an expansion valve system. The liquid line is also the line that connects the condenser coil and the orifice tube together in an orifice tube system.

Magnetic clutch - The magnetic clutch is a device which is used as a coupling. The coupling turns the compressor on and off.

Manifold gauge set - The manifold gauge set is complete with gauges and hoses that are used to measure the pressures in the air conditioning system.

Moisture - Moisture is water in the air or water that is in the refrigerant.

Moisture indicator - The moisture indicator is the device that uses color to display if the material in the dryer is fully soaked with moisture. The moisture indicator will display a pink color if the moisture indicator is soaked with moisture. The moisture indicator will display a blue color if the moisture indicator is capable of absorbing more moisture.

Overcharge - Overcharge is having too much refrigerant in the air conditioning system.

Partial charge - A partial charge is less than a full charge of refrigerant put into the air conditioning system.

Performance test - The performance test is the notation of temperatures and pressures under controlled conditions, that determine if the air conditioning system is operating normally.

Refrigerant quick-check procedure - The refrigerant quick-check procedure is a fast check without the use of instruments.

Receiver-dryer - The receiver-dryer is the component in the air conditioning system that removes the contaminants (moisture) from the circuit.

Reclaim - The reclaiming and the restoring of air conditioner refrigerant must meet the SAE specification and the ISO specification. Air conditioner refrigerant can only be reclaimed at a remanufacturing facility.

Recover - Recovering is the removal of the air conditioner refrigerant from the air conditioner system and storing of the refrigerant in an approved container. The removal of the refrigerant can be done without necessarily testing or processing the refrigerant in any way.

Recycle - The recycling of the refrigerant is usually completed at the site or at the service shop. The refrigerant can be cleaned by separation of oil. The refrigerant can be cleaned with passes through the filter in the dryer.

Refrigerant - The refrigerant is the fluid that is used in the air conditioning system that removes the heat from the operator's compartment.

Refrigerant oil - Refrigerant oil is the oil that is used in the air conditioning system.

Sight glass - A window that allows refrigerant flow to be observed

Stabilize - If the system is constant, the system is stabilized.

Stuck - Sticking will cause the prevention of free movement.

Subcooling - The additional cooling of the refrigerant in the bottom of the condenser after the refrigerant has charged from vapor to a liquid.

Suction side - The suction is the connection that is between the evaporator coil and the compressor.

Superheat - The additional heating of the refrigerant in the bottom of the evaporator after the refrigerant has changed from a liquid to a vapor.

Vapor - Gas

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