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Mazda Protege5 Alternator issues

Thanks for taking time to read! I replaced the alternator in my 03’ Mazda Protege5 in February 2019, and now it has seemingly failed within 9 months. Or so I thought. After looking at replacing it, I saw that the main connection (of which I believe is the one that leads to the battery itself) has melted/burned apart. I’m not able to take the plastic casing off because it has melted together. I don’t have extensive car knowledge, however I can usually replace things like brakes, alternators, valve cover gaskets etc. what I guess I’m asking is, is should I try to fix this? I believe it’s above my pay grade. Also what could have cause this? And lastly, do you have any other advice? Thanks so much. PS this all seemed to happen only within a matter of about 50 miles after replacing my valve cover gasket, which I believe to be unrelated however, if it is potentially related, let me know please. Thanks!

Something got very hot and melted those connections.

All you can do for now is, disconnect the battery, take a pair of Channel-Lock pliers and crush the melted plastic to remove the connections.

Then maybe you can figure out what caused that much heat, and what it’s going to take to replace the melted connectors.


When replacing alternator, did you have the connection properly cleaned, covered with electrical protection grease and then torqued to the specified force?

If not, what might have happened is that the contact point had resistance above normal, resulting in overheating and eventual failure.

The current in that connection is measured in tens of Amps (sometime 100 and above), so even 0.1 Ohm resistance will result in substantial heat generation

It appears to me that the metal shield over the output bus bus bar was pushed and bent into contact with the stud it was meant to protect.

If the burn damage is just limited to the connector then the trouble was most likely due to a bad connection between the alternator output stud bolt and the main wire terminal. If there is signs of insulation damage along the wire itself then that would mean a possible short on the line happened somewhere down the wire and before the fuse. Make sure the battery condition is good. A shorted cell inside the battery could cause bad stuff like this to occur.