Could it be the thermosat?

I have what seems to be a short in the freezer of my side by side. My question is could the thermostat be my problem? I turned the defrost control on the lower bottom of the frig. And put the unit in defrost the heater came on and defrosted the condenser coil. Then I turned the defrost control again to get out of the defrost cycle and the breaker blew. At this point you can’t reset breaker but if I continue with turning the control the ref. comes out of this cycle and you can reset breaker and everything works fine.