It sounds like there may be a 12v wire which has rubbed through the insulation and is shorting to ground. Maybe the grommet is broken. IMO, you need to look carefully at this section of the harness with the battery disconnected to find the short. If it was visibly melting, you have the very real possibility of a fire. You may be well advised to take it to an auto electrical shop and have them check it out. Have it towed there of course. Very dangerous situation you described. My .02 Mike 
'99 Sport TropicGreen,Duratec, SVT exhaust, Brembo rotors, Ceramic pads, K&N filters(oil & air), Alpine CDM7874, Polk DB570 speakers front and rear. Fog light mod. 50% Formula One tint.
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