Graphics card fans are not spinning

Hello,
I've been building my computer outside the case today and I've discovered that when I power it up the graphics card fans don't spin. They start to but then stop immediately. The fan on the CPU spins and the power supply appears to work. I have tried to move the card to another pcie slot and it is plugged In. Any suggestions?
Specs:
CPU- amd fx 8 core processor
PSU- sea sonic M12 II bronze
GPU- gigabyte amd radeon hd 7870
Mobo- asrock 970 extreme3
Memory- ballistix 8 gb DDR3 1600

Thanks