I had a similar problem with a different model Norcold with electronic controls. I was told that it was most likely ac ripple current in the 12 volt dc power. My rig had an old magnetek converter in it and I replaced it with a new Progressive Dynamics converter. It solved the problem.
I believe that someone earlier in this thread mentioned that it sounded like this very problem. I'm sure my old Magnetek converter had bad filter capacitors that were letting in the ripple current and the new PD converter solved it.
I'm not a tech person, but I believe you can test for the ripple current by checking the 12 vdc voltage with a digital meter set on the ac voltage setting. Hopefully someone else can tell you exactly how to do a test for the ripple current. Good luck-- Mick
2007 Itasca Suncruiser 35L
2000 Jeep Wrangler