The AC is not working properly. THe unit turns on, the fan turns on, however, there is no air flow. Checked unit outside and the line coming from the AC unit is frozen over.

Will this cause the air flow to stop? If so what is the problem with the unit that it's freezing, once it defrosts... the air starts flowing again.

Help! I'm hoping this is not costly to repair.

Thank you

Will this cause the air flow to stop?

Yes

If so what is the problem with the unit that it's freezing, once it defrosts....the air starts flowing again

The unit might be low on refrigerant, the air filter could be completely blocked or very dirty,the inside air vents and return air could be blocked/closed or the outside temperature at night has dropped below 55 or 60 degrees allowing the drop in head pressure to cause the freezing. This causes a low ambiant condition. More than likely your unit is low on refrigerant,
If you turn the outside unit off and leave the inside blower run it will defrost easier. Usually 2 to 3 hours depending upon how bad the indoor coil is frosted or iced over to start with.

Once the unit is defrosted you can start up the outside portion (condensing unit) again and see how it performs. You will eventually need to call for ON SITE service since this problem will not correct itself.

Check your filter first. If it is very dirty, this may be your problem. Also if your filter isn't changed often enough, your evaporater coil may be clogged. Clogged evap coil can also cause problems with the operation of furnace. Everything that hvac said was dead on. If you are low on refrigerant, or it is anything more than a dirty filter or evap coil, I would also recommend a hvac tech(must be licensed to work with refrigerant) Hope its just a filter, and good luck.

Please let us know what you find.

Thank you for both of your help.. the AC unit was low on freon, there was a slow leak because the gasket in some suction cap was twisted and was pushing on something that caused the leak. He also shifted the dampers, checked filter and added some freon. The unit is working now.

Sounds like your schrader valve was leaking. Glad to hear they located the leak before recharging. Take care

This is a perfect example of why I use Leak Loc on enerything lol.

Glad you got it going