Having read this report many times and experienced it once you have cured the symptom of low refrigerant but not the reason as to why it is/was low. Try sniffing around your high and low service ports. Our '01 needed the port seals done 10 years ago. The kit supplied by the dealer was reasonable and updated the valves to the common type found in most modern systems that can have the "O" rings replaced as and when required. If it is not a service port problem then it could get expensive in a hurry.

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