imac wont power on after power outage

Hello, My IMac Mid 2011 I5 won't power on after a power outage it will completely go dead or even when i shut it down and i want to power it on the next day it won't power on. I have to open my IMac and heat with a heat gun the PSU (power supply unit) and then i will power on after it have reach a certain temperature. otherwise it won't boot or make any sound that is the only way i have found to make it work if you guys have any solution for this i would highly appreciate your help.