HPI V3 speed controller turns itself off!

[aceracer]

hi everyone
i'm just woundering if anyone has had this problem or knows how to fix it.
ever since i got my v3 speed controller if i stop the car moving e.g start line or final grid the car turns itself off and i have to go and press the button again to get it on i've tried changing lipos,servos,motors,pt,and reciver and just nothing seems to be working if i am driving all the time non stop it doesn't turn off it's just when i'm at a stand still
hope somebody knows how to help thanks