A/C not working 3 yrs What is highest $$ for total replacement of A/C?

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A garage no longer in business worked on my air conditioning system and it never worked afterwards. (I paid over $1,000.) I have no clue WHAT is wrong - have been afraid to take it anywhere since. Afraid to be taken advantage of again - but this 90+ weather is really horrific. Car only has 64,000 miles. Thanks for any help!