melted ALT 1.25B

[daveh1961]

Hello,, we have a 1987 toyota supra, and we had a slight melt down in the fuse /relay box located under the hood. The ALT 1.25B was melted. we checked the alternator and found no issues.(it passed the testing) We were trying to purchase a new (either fuse or relay) uncertain. Hat is why I am trying to understand just what this device is. And the second was what would cause this to just melt down if te alternator is not bad.

thanks