HELP - Canon AE-1 wont make the len's aperture work.

[tchosjdr]

I have tried everything.
I am very familiar with the Canon AE-1 but i cannot figure out why the len's blades are not closing.
The lens works when i put on another Canon ae-1 body.
The lever responsible to close the leans blades seems to move strong when i press the shutter with the lens unattached, I can feel with my fingers that it has power to close the blades.
When I move that black little switch on the left side of the body(front, left) the blades close. But when i let the switch go the len's blades open and everytime the shutter goes off the len's blades won't close.
Help Camera geeks.
Thank you