Air Conditioning - ac not cooling

my first post here and I'm trying to understand ac problems. I live in Houston, TX where it's already getting hot.

In the past year, I've had four service calls on my ac unit. Each time the a/c unit blows, but does not cool the house. The first three have been due to coolant leaks (the coil in the outside unit was frozen). The a/c repair co. came out and added coolant (forgot how many gallons).

Today I have another call. The a/c unit is flowing but not cooling. Unlike my other problems, the coils were not frozen.

Each time the a/c repairman tells me the unit is in good shape and running well. I have a hard time believing that b/c it's now the 4th time in a year to have repair come out.

I have a Trane unit, about 10 years old. My question is this: are these types of problems a sign of a bigger problem with the a/c?

No Pro..but you have a leak which should have been found and fixed before anything was added. If the tech came out a second time w/in a year and added even more refrigerant, and says your unit is in good shape..he's just sucking money out of your pocket.

Frozen coils are a sign of low charge of refrigerant, sounds like you don't have ANY left this time.

Don't run it until you find a company who will find the leak and repair it, if possible.

At ten years of age AND living in Texas it may pay to have the entire system replaced with a high-efficiency system. There is a tax credit of (I think) 15% of the total cost to a maximum of $1500. The percentage may be a bit higher.

The operating costs will be significantly lower with the new system and comfort may also increase.