Hi I need help please. I just had a 4 ton reem and a coil andnordie furnace installed yesterday. And its only 90 out side and my house won't get below 80 during the day. At night it works good. My house is. A 1987 oakcreek mobile home 1280square feet. Someone plaza tell me what it could be. It seems cold coming out of the floor vents and its blowing pretty hard. And I have a shingle roof whitch I don't think us vented but I did have a four ton installed

4 ton for that sq. ft. seems extremely large. I have a 3,000 sq. ft. house with a 4 ton and it is very adequate. A lot depends on insulation and MH's, particularly older models, are not usually well insulated. Shaded? Ceiling get hot in the daytime? Since it is working OK at night would lead one to believe your issue is radiant solar load and AC won't cure that.

2.5 to 3 ton ac is the most you should need,, you going to end up with a humidity/mold/mildew problem,, and I agree with ma0641 you probably have a insulation problem

"Seems cold" doesn't tell us a whole lot. Actual supply & return temps would help. The return temp can be taken in front of the furnace door. This presumes the furnace fan blows the air for the A/C.
If the A/C is a package unit (does not use the furnace fan) you should have 1 or 2 large return vents in the floor. They will be about 14" x 22". Measure the return temp there.