[chadsapp73]

My AC IS a 3.5 ton split I'm having trouble with it blowing cold air for more than 2 hours at a time what cold cause this when it starts up after about 30 min. its blowing 49.6f and after about another hour and a half its blowing 66. f. there is no sign of freezing up and the coils have been cleaned and it has a new filter what else can I do ? At it's best in the 2 hours there is a 20.f Degree difference and at it's worst it is only 6.8f.

[zanec]

My AC IS a 3.5 ton split im having trouble with it blowing cold air for more than 2 hours at a time what cold cause this when it starts up after about 30 min. its blowing 49.6f and after about another hour and a half its blowing 66. f. there is no sign of freezing up and the coils have been cleaned and it has a new filter what else can i do ? At it's best in the 2 hours there is a 20.f Degree difference and at it's worst it is only 6.8f.

Sounds like the contactor is faulty and won't pull out shut the system down so then the condenser runs until it shuts down on low pressure cut-out but let the pros answer and see it they have the same answer.

[letmetellu]

One cause for what you describe is an over charge of freon but it has to be over charged to a high level to be as noticeable as you say.

A 20 degree differential is good 17 to 18 is as low as you really want.

Another cause could be a problem with an expansion valve that meters the amount of freon that goes through the evaporator coil.

Off hand those are the only two that come to mind without more information about the units run time and some gauge pressures.

[Joshdta]

Could maybe be a condencing fan motor going bad and shutting down.