Air Conditioning and Heating R-12 All Caterpillar Machines – Refrigerant Compressor Oil – Check

------ WARNING! ------

Personal injury can result from contact with refrigerant.

This system is under pressure at all times, even if the engine is not running. Heat should never be applied to a charged system.

Contact with refrigerant can cause frost bite. Keep face and hands away to help prevent injury.

Protective goggles must always be worn when refrigerant lines are opened, even if the gauges indicate the system is empty of refrigerant.

Always use caution when a fitting is removed. Slowly loosen the fitting. If the system is still under pressure, evacuate the system recovering the refrigerant before removing the fitting.

Personal injury or death can result from inhaling refrigerant through a lit cigarette.

Inhaling air conditioner refrigerant gas through a lit cigarette or other smoking method or inhaling fumes released from a flame contacting air conditioner refrigerant gas, can cause bodily harm or death.

Do not smoke when servicing air conditioners or wherever refrigerant gas may be present.

Before any checks of the air conditioning and heating system are made, move the machine to a smooth horizontal surface. Lower all implements to the ground. Make sure the transmission is in neutral or park and that the parking brake is engaged. Keep all other personnel away from the machine or where they can be seen.


A special refrigerant oil is used in the air conditioning system. The oil mixes completely with the refrigerant so that all the components receive lubrication. A check of the refrigerant oil in the compressor will give an indication of the amount of oil that is in the system.

Reference: Refer to System Operations, “Refrigerant Compressor” for more information.

Note: Generally, the oil in the compressor is checked when there is evidence of a major loss of oil. The following conditions may cause the loss of oil:

  • Broken refrigerant hose

  • Hose fitting (leaks)

  • Badly leaking compressor seal

  • Component damage

Complete Check of Compressor Oil

When the replacement of a component is necessary, follow the procedures below. The procedure determines the amount of refrigerant oil (lost oil) that is needed in the compressor.

  1. Operate the engine at 1000 rpm. Set the temperature on maximum cooling setting. Move the fan speed switch to HIGH. The system will stabilize in a minimum of 10 minutes.
  1. Stop the engine. Remove the refrigerant charge from the system. Install a plug in all open lines. Refer to Testing and Adjusting, “Refrigerant Recovery” for the proper procedure.
  1. Remove the compressor from the machine. Place protective caps on all fittings and hoses.

    Illustration 1 g00296421

    (1) Pulley

    (2) Hose (low pressure)

    (3) Hose (high pressure)

    (4) Electrical harness

    (5) Service valve (low pressure)

    (6) Service valve (high pressure)

    (7) Plug (oil change)

    (8) Belt

  1. Place the compressor in a horizontal position so oil plug (7) is facing downward. Remove oil plug (7) from the compressor. Drain the oil into a clean container. Rock the compressor back and forth in order to remove all of the oil. Also, rotate the compressor shaft in order to drain the rest of the oil that is in the oil sump. Inspect the oil for the following items:

    • Contaminants

    • Metal chips

    • Rubber particles

    • Foreign material

    Dispose of the oil in a suitable manner. Use the following list as a guide for adding oil into the compressor:

    • If the amount of oil that is drained from the compressor is 118 mL (4 fl oz) to 237 mL (8 fl oz), put only 118 mL (4 fl oz) of oil back into the compressor. Never add more than 237 mL (8 fl oz) of oil to the compressor.

    • If the amount of oil that is drained from the compressor is less than 118 mL (4 fl oz), add new refrigerant oil. The total amount of oil in the compressor should not exceed 118 mL (4 fl oz).

    If too much oil has been added to the system and a total of more than 325 mL (11 fl oz) of oil is in the system, the cooling capacity of the system will be reduced. If too little oil has been added to the system, the compressor may fail due to a lack of lubrication.

    If the failure of a component causes particles of metal or other foreign material to be present in the system, it is necessary to flush the system. Refer to Troubleshooting, “Air Conditioning System Troubleshooting” for the proper diagnostics.


    1. When possible, add oil to the compressor through the opening for the oil plug (7). If the oil cannot be added through the opening for the oil plug, inject the oil through the discharge port that is for charging. The compressor must be positioned so that the refrigerant oil will not flow out of service valves (5) and (6). Do not rest the compressor on the compressor shaft. Turn the compressor shaft by hand when you fill the compressor. The oil will slowly flow into the compressor. Only use refrigerant oil that is approved and recommended.
    1. Add oil to any components that are being installed.
  1. After the correct amount of refrigerant oil has been added to the system, install the compressor and the drive belt. Refer to Testing and Adjusting, “Refrigerant System – Charge” for the proper procedure.
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