Air Conditioner frosting at the bottom
It seems like a contradiction, but ice on the inside coil almost always means the air conditioner is LOW on refrigerant.  Most people think freezing up would mean too much, but in the case of AC it means the opposite.  

It takes a physics lesson to explain why,  but in short because it’s low there is not even cooling across coil, instead too much cooling occurs in one spot and not enough across the rest of the coil.  That’s an over-simplified explanation, but to the point.

At 7-10 years old, I wouldn’t try to get that unit repaired, replace it instead—the new one will be more energy efficient and save you on electricity, todays units use significantly less electricity in most cases.