My AC is frozen. What should I do?

Ice on the copper line outside, or on the indoor coil if you can see it, means the evaporator has dropped below freezing. That happens for one of two reasons: not enough warm air is passing over it, or there is not enough refrigerant in it. Either way, running it frozen can take out the compressor, so the first step is to switch cooling off at the thermostat and set the fan to run, which thaws the coil in an hour or two. Put towels under the air handler; the melt has to go somewhere.

While it thaws, change the filter and check that every supply register in the house is open and nothing is blocking the return grille. If the filter was badly clogged or half the vents were shut, that was probably the cause, and once it is thawed it may run normally.

If the filter was clean and the vents were open, the likely cause is low refrigerant, which means a leak, or a failing blower motor, and both need a technician. Do not keep thawing and restarting it; each freeze is another chance to flood the compressor with liquid.