Hi all =)  got a problem whit my antminer s7

It was working fine for months wihout problems, then it just didnt want to hash anymore.. Now when i start it , it hash for 5 minutes then it looks like it freez totaly all the fans are working at100% but it wont hash. Then a restart it again and it hash for 5 mins and then it kinda freez again no hashing but fans are running at 100% and all the small green lights are on

anyone have a clue what this could be ?