So before freon recharge ok ang idling mo. After recharge fluctuating na. If I were you I'd go to another aircon shop and have my system checked. Maraming pwedeng reasons. Pwede dumikit ang condenser sa radiator. Pwede mahina ang aux fan. Pwedeng overpressure dahil nasobrahan sa freon. The servo should be the last resort dahil, yun nga, mahal sya.