How old is this Yaesu? Where was it before starting to act as it does now? Did you just get this radio from someone and they showed you it worked ok? Give us more infor about the radio if you can.
And what do you mean, it acts like it is shorting? Sparks flying, loud poping noise, etc.
Hey it is not that old may 6 months old it it trips the power supply when you hook up pos and neg to power supply or it pop the fuse if you hook it up in truck no arcing or anything I have google on here it mentions it has a protection diode not sure if that's the problem
Many mobile radios today have a large reverse polarity protection diode inside of them. I would open it up and look for a big diode near where the power comes into the radio. Take an Ohm meter and read the resistance in both directions. (swap the meter leads for the second reading) If you get the low resistance in both directions, it is blown or shorted as many people would say.
Next step is to cut one end of the diode loose and see if the radio will power up. Hopefully it is not a surface mount component. There is no guaranty that the radio survived having the reverse power applied to it. But that is why the big diode is there to blow the fuse and protect the radio from some dummy that didn't know plus from negative when applying power to the radio.
Good luck and hope the radio still works. Let the group here know what you found. Then go back to the person who sold you a dead radio and tell him "Thanks a lot".