Changed a 4 ton to a 5 ton unit in a mobile home uped duct size 12 to a 14 feeding other side of moblie home . It is freezing up what could be going wrong

Unit is too large for the home. You overdid it with the size. Unless the home is enormous - like 28 X 80 it is too large for the home. What size home is this? I had an enormous double wide in South Florida and I only had a 3 ton unit and it did the job just fine. A 5 ton unit is more for a huge house.

Even if you changed the main trunklines and added vents to maybe add on rooms,that is a very large a/c unit,even for the new double stacked modulars