The expansion valve is defective (Worksheet 3)

Note

The expansion valves bulb is always installed on the evaporator’s outlet tube (suction pipe) (1/2″ pipe).
On expansion valves with external pressure equalization, the following test must be performed while the system is running:

  • Allow the temperature sensor to cool.
    You should be able to note a reduction in the high and low pressure.
  • Allow the temperature sensor to warm up.
    You should be able to note an increase in the high and low pressure.

If the expansion valve does not respond to the load described, there is a fault.
Check the expansion valve further in the manner described below.

The expansion valve's bulb filling is defective.

  1. Draining the refrigerant from the air conditioning system.
  2. Replacing the expansion valve.
  3. Removal of the non-condensible gas in the air conditioning system, which means that the vacuum pump is kept running for at least 30 minutes. Important: Check the degree of evacuation!
  4. New filling of the air conditioning system with the recommended amount of refrigerant and oil, if there has been an evacuation of the refrigerant (see the assembly instructions or the refrigerant table).

The mechanism in the expansion valve is blocked

  1. Draining the refrigerant from the air conditioning system.
  2. Replacing the expansion valve.
  3. Removal of the non-condensible gas in the air conditioning system, which means that the vacuum pump is kept running for at least 30 minutes. Important: Check the degree of evacuation!
  4. New filling of the air conditioning system with the recommended amount of refrigerant and oil, if there has been an evacuation of the refrigerant (see the assembly instructions or the refrigerant table).

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