MacBook Pro late 2013 Freezes at login screen, but it doesnt if I conn

Hi, hopefully you can help me, i have a macbook pro late 2013 retina display, that is freezing when entering user and password, however if i connect a external monitor it works just fine, no freezes, i was reading and it looks like its a screen issue (maybe overheating or any sensor idk), wondering if you guys have some solutions, unfortunately i dont have another screen to try it out! .

PS: I did a full mac os sierra installation, i ran techtool pro and everything was ok, until it get to the login screen or when installation finished and you get to the welcome screen to set your mac up for the first time!

thanks