Our engineers have already checked and tested again as below;
1. Checked battery voltage was 0.4 V then they changed battery.
2. Connected gram data logger program with laptop (Window 7) by Com-to-USB adapter. They still cannot connect the program but the display did not show alarm and error message.
3. They tried to connect with PC (Window XP). Same result 2 cannot connect the program but the display did not show alarm and error message.
4. They set temperature at -2C but on display showed -2C about 30 seconds after that return to -1C and took a lot of time to show -2C again. Is it normally?
5. They checked four ports (yellow, green, red, black) of refrigerator but they found only red line connect for RS232.