Dealing with an unhelpful and unresponsive thesis advisor? My thesis advisor is based on another city and we barely had meetings during my master thesis process.  At most three times. He responds very late to my emails and I have to wait weeks sometimes. 

But the deadline is approaching and he has to give feedback to me. 

(Instead he advised me to find a second advisor from where I work to continue quickly with her and that person helped me ten times as much as the actual advisor did!) 

When should I remind him about my emails and that I'm waiting for his feedback? I know they can be busy but I was too alone and isolated in this process except the guidance the second advisor from my workplace..
Ideally, you should make an appointment and meet in person with your advisor. If this is not practical you could send an email to propose a skype meeting or a phone call. 

If they don't answer your emails, wait at least a few days and preferably a full week before sending a reminder. If there's really no answer after a couple weeks and the matter is urgent, then try to call them directly in their office (during office hours).