Final stage unit question
 

My blower has been acting up so I got a new fsu. It worked for about 15 minutes and then went out. Every time I drove the car I got about 15 minutes but also the max would not work. I returned part since I thought it was defective. Received new fsu and now have the same problem. It doesn't work on max and it stops working frequently. Do I have another bad fsu or is something else wrong with my blower? When it is blowing it blows great without any noises. I find it hard to believe I got two bad fsu's back to back. The fsu brand is sitronics.

Any suggestions? I tried to clean the connections with a pipe cleaner. Didn't help.