We are having trouble with our home Central Air unit. Our air has been running really cold all summer long and then suddenly one day we noticed it was warm in the house. Upon inspecting the unit we noticed that the larger copper line was frozen all the way from the house to the condenser as well as the evaporator coil in the inside air handler.

We have replaced the outdoor fan and the capacitor is fine. The system was installed in 2003 and the evaporator coil was replaced in 2005 or 2006. The filters had been recently cleaned prior to the problem starting, but they had been neglected for several months prior. We can run the unit for a couple of hours and the temperature will lower a few degrees, but then it begins to freeze over again so we allow it to thaw again. I have continuously checked the temperature coming out of one of the vents and when the air is running the temp is usually 64 to 65 degrees F even when it is 85 degrees in the house.

We are trying to figure out what the problem may be prior to contacting a professional. I would greatly appreciate any information or advice that anyone can give me. Thanks

YOu need to contact a professional... because I believe one of two things is going on... #1 the refridgerant charge is low... and/or you might have a worn compressor.

These are not designed to run continuosly... and need the off time between cycles in hot and humid weather to prevent ice buildup.

If either condition esists it runs constantly attempting to cool the house.. and once ice starts to form it rapidly developes a huge icecube... preventing it cooling the house even though it keeps trying to.

Turn it off... let it thaw... and call for an appointment

I beg to differ with Smoothy. They do not need off time. When it's hot outside, my system will run up to 22 hrs. straight without shutting down & without ice formation. Only two things will cause an A/C system to freeze. They are (1) insufficient air flow through the indoor (evaporator) coil & (2) low on refrigerant.
I will agree with Smoothy's advice to shut the system down, let it thaw, & call a pro.