I had replaced 2 motor resistors in the past 2 months and on this third one I noticed a solder joint that had came apart.Is that a built in type of a fuse and that would mean I have a short somewhere or is it a bad design or a bad part again.I resolder it and for right now it works.
I replaced the blower motor because it was the reason the relay got too hot.
BAD SOLDER JOINT

REsolder the joint

 

id say check all the wires, maybe a bad ground

 

sounds like somethings causing it to heat up too much ....could be poor wiring connections causing too much resistance.