A blown mega-fuse will prevent the battery from charging. The alternator light will always be on. The engine will start and all electrical accessories will operate - as long as the battery has a good charge (not too long usually).
On common way of blowing the mega-fuse is to connect the battery backwards or to connect jumper cables backwards.
The fuse has a big strip of metal that is easy to see and check if it is blown. It is located behind the rear valve cover - look for thick cables running behind the engine
If this is the problem, it basically means your mechanic is incompetent in the extreme.
99 Tropic Green SVT, Tan Leather, 20K miles, "Nice Twin" (factory stock).
99 Tropic Green SVT, Tan Leather, 28K miles, "Evil Twin" (Turbo AER 3L and more in progress)
96 Red LX, Opal Grey Leather 2.5L, ATX, 22K miles
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