I have a 87 firebird 305. My idle has recently been really bad, dropping low then eventually dieing. However tonight the positive battery cable, the smaller red wire connected to the larger one, the smaller one overheated and actually broke the connection. After the connection was broken the car was idling fine, however the battery wasn't charging because the alternator was disconnected. So is it just a bad alternator? or does anyone have any other ideas? Thanks in advanced for the replies!

 

I had a dead alternator on a friend's ford ranger. Same issue. It ran a couple seconds, then died. I charged battery, it ran 15 minutes, then ran rough and died. I changed alternator and problem was fixed.

 

You can take out the alternator and have advance or autozone test it for free. Or you can get that wire fixed and take the whole car and they'll test it in the car.

 

so i replaced the alternator and i still have the same problem, the wire from the battery cable also keeps over heating, it melted the connection once already, when i am running lights or a/c. Also i realized today that the rear defrost can only be on for a few minutes before it cuts out. Any ideas? i'm thinking it might be the epu? but i don't really know! any help is much appreciated thanks for the replies too

 

Since you now know the old alternator is probably good, save yourself $100 and return the new one you put in. I believe the rear defroster is suppossed to "time-out" and shut off on its own after a couple of minutes, so that may not be a big dea (maybe someone else can comment on this, because my defroster never worked in the first place). Having a wire constantly overheat...that sounds like it may be grounded somewhere. Try following the wire along, if it melted in one spot, it may have melted in others. Also, try to run the car at night with no lights around you. Look for arching under your hood around wires.

 

I'm assuming you mean the ECM (computer - Engine Control Module) - The ECM has nothing to do with the charging system, or anything electrical except for engine sensors.

You have some issue with the alternator/starter/battery wiring for sure - something is grounding where it shouldn't be, or something is not grounding where it should.

Grounds should be
1) batt neg to car body close to battery
2) batt neg to motor close to alt
3) motor to body at pass rear of motor

Rear defrost cuts itself off after about 5 minutes.