[xrated]

Evaporator freeze up is usually a sign of one or more things
1. Not enough air flow across the evaporator.
2. Freon charge is low.

Not enough air flow could be something as simple as the fan speed being set on low speed instead of high speed, especially if you are trying to operate the unit in very high humidity conditions. It could also be a dirty evaporator which doesn't let enough of the return air flow across it. Another possibility is having some of the outlet air vents closed off....if you have the type of outlets that allow you to close them off or almost closed off.

Number two possibility ( low refrigerant) means that there is a leak in the refrigerant circuit. This could be in any of the components.....evap, condenser, any of the tubing, compressor lines, etc. If there is a refrigerant leak, it is usually cheaper to buy a new A/C unit than to have the existing one repaired. They don't usually come with service ports installed when new, and when you add the cost of adding them AND fixing the leak, a new unit is a cheaper option usually. Check the easy stuff first....air flow issues. It could also be a fan that is dirty or the brains are failing, causing the fan to run at a reduced speed, thus not enough air flow.