Norcold 1210 IM Blows 5 amp fuse

I replace the cooling unit on my Norcold 1210 IM..... everything went fine. Unit worked great. The outside temp dropped below freezing, Ice maker line broke spraying water all over the motherboard tripping the 30 amp AC circuit breaker. Reset breaker. I could not get the unit to work. I replaced the motherboard. Everything went fine. Unit worked great. Almost too great. I had to turn the setting down to 1 to keep the milk from freezing. Blew the 5 am DC fuse a couple of weeks later. Replace it. Unit worked fine. Same fuse blew a few weeks later. Replaced it. Unit worked fine. Now, a few weeks later, the fuse has blown again. I cannot put another fuse in without it blowing immediately. Help? Thank you!