Chevrolet Full Size Cars 1979-1989

Expansion Tube (Orifice)


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Fig. Fig. 1 Air conditioning system schematic early model vehicles

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Fig. Fig. 2 Air conditioning system schematic late model vehicles

The factory installed air conditioning systems for vehicles covered by this guide utilize an expansion tube (orifice). The orifice is used to regulate the flow of refrigerant to the evaporator, so is placed somewhere inline between the condenser and the evaporator. It is designed to ensure that the evaporator remains as full of liquid refrigerant, as possible without allowing any liquid to pass into the compressor suction line. The orifice is usually found in the evaporator inlet, but is relocated on some models to the connection at the condenser.


Please refer to before discharging the compressor or disconnecting air conditioning lines. Damage to the air conditioning system or personal injury could result. Consult your local laws concerning refrigerant discharge and recycling. In many areas it may be illegal for anyone but a certified technician to service the A/C system. Always use an approved recovery station when discharging the air conditioning.

  1. Properly discharge and recover the refrigerant in the A/C system using a suitable recovery station.
  3. Disconnect the negative battery cable.

On some models, the orifice tube has been relocated from the inlet of the evaporator to the connection at the condenser. The relocated orifice tube can usually be seen by looking through the driver's side grille opening.

  1. Loosen the nut holding the liquid line to the evaporator inlet pipe. Remove the tube using needle nose pliers
  3. If the tube is broken or difficult to remove:
    1. Using a heat gun, apply heat approximately 1 / 4 in. from the inlet pipe dimples.

If a pressure switch is located near the orifice, remove it before applying heat so as to prevent damaging the circuit.

    1. Using a twisting motion, loosen the orifice tube and remove it from the holder.
    3. Make sure the inside of the evaporator pipe or condenser is clean and free of debris. To install:

  1. Lubricate the new orifice tube and O-ring using clean refrigeration oil.
  3. Install the orifice tube. If installing the tube to an evaporator inlet pipe, be sure to position it with the shorter screen end inserted first.
  5. Install the liquid line to the evaporator inlet pipe.
  7. Connect the negative battery cable.
  9. After checking that all the refrigerant lines are properly tightened, evacuate, leak test and charge the system.