Incubator blowing through fuses

I have an Isotemp 304 incubator which received a new fuse in 2015 and has stopped working since. I recently put a new fuse into one of the three fuse ports only to see it run and then fail again shortly thereafter- within minutes. Does anyone have some ideas how to proceed? I'm thinking there is a short somewhere but not sure how to sluth that out. Thanks!