Any ideas?

[HeavyMetal]

So, after spending a small fortune putting his pathy back together from a snow wreck, we're chasing some unrelated electrical issues.

We realized after a week of dead battery issues, the darn alternator tensioner assembly was gone. So we replaced all that, a new battery, and still, we were fighting a dead battery. We finally had the alternator tested and it was putting out half of what it needed. However, after replacing the alternator, we have nothing happening at the ignition. When you turn the key on, you have no fan, engine lights and starter. THEN, he tells me the last time he tried jumping it, he had the cables on backwards.

So what could we be looking at here? Fried computer? Ignition? Main relay? Any ideas would be appreciated. There is some electrical coming on, but not what normally would. Fuses all look good.

[Slartibartfast]

Backwards cable ain't good. IIRC there's a safety relay that should've protected most things. First thing I'd check are the fuse links hanging off the + battery terminal--the plugs with a loop of wire that goes out of the harness and then right back in again.