Why does car keep blowing 40 amp fuse? on 1995 Pontiac Grand Prix

Car is slow in acceleration; windows won't roll up/down; AC won't come on-the fan blows but only out the top & bottom vents. The car has 208K miles on it. It has been running well. Spent $900 to have extensive electrical tests done, but it didn't fix the problem. My wife drove off the lot and problem returned. I won't take it back to mechanic until I get specific info of what problem might be.

Asked by for the 1995 Pontiac Grand Prix
Short circuit, but no way we can tell where it is without seeing and checking it. What circuit is this fuse listed for?
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For $900.00 , what's the rest of the story?
Sorta curious myself!