In the past few months, I have had the in-line fuse holder to my meziere water pump melt twice! the fuse doesn't blow, but the holder just melts away.

I put a Kragen replacement, so I don't know if the contacts (spring->fuse) are good enough to not create a hot spot.
The other option I am leaning toward is the pump aging and drawing more current to turn.

Has anyone ever had this problem before?

 

Mine didn't melt the fuse holder but one day I noticed it was very hot though the rest of the wiring wasn't. The manufacturer had crimped the brass contacts in the fuse holder to the wires. I pulled them out and soldered them. After that the holder was no warmer than any other parts around it. Still fine years later. Or you could try one of the heavy duty after market "blade type" fuse holders. No spring that might weaken and cause less than adequate contact.