Canon fd 50mm 1.8 strange aperture problem

Hi, I just purchased a canon ae-1 program with an fd 50mm 1.8 sc lens and I realized the aperture ring wasn't closing so I did that process where you take the lens off, poke the button, and rotate the ring to manually check the aperture. It opens and closes smoothly but for some reason it just won't close when I put it back on the camera and click the shutter. I have flicked and pushed every button and lever to make sure it's not a quirk or mistake I made. Is it a bad lens? By the way, I tested the same lens on another ae-1 and a different lens on the original camera and the different lens worked. Thanks, sorry if the answer is obvious.

Is the automatic diaphragm lever, the one at the bottom of the mirror box, in the idle position when you mount the lens?
If it is in the stopped down position before mounting, red dot behind the lever showing up, it cannot close the diaphragm.

AgX said:

Is the automatic diaphragm lever, the one at the bottom of the mirror box, in the idle position when you mount the lens?
If it is in the stopped down position before mounting, red dot behind the lever showing up, it cannot close the diaphragm.

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Sorry I worded the question completely wrong. I meant the aperture *blades* don't close when the lens is mounted. Sorry for the bad wording I'll try to fix it. Thanks for responding.

JCook0113 said:

Sorry I worded the question completely wrong. I meant the aperture *blades* don't close when the lens is mounted. Sorry for the bad wording I'll try to fix it. Thanks for responding.

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In other words, if you pull the lever manually when the lens is detached, blades remain open?

If yes, then might be dried oil, or might be a fault in mechanism itself. Either way I reckon you might need to disassemble the lens.

M-88 said:

In other words, if you pull the lever manually when the lens is detached, blades remain open?

If yes, then might be dried oil, or might be a fault in mechanism itself. Either way I reckon you might need to disassemble the lens.

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No when I manually pull the lever when the lens is detached it does close but when it's on the camera and I click the shutter they won't close no matter what I do. Thanks.

The camera's diaphragm actuating lever is either not working at all or too weak to actuate the lens diaphragm lever.
Look at the camera's lever while the shutter is fired. See if it moves when no lens is mounted.

JCook0113 said:

No when I manually pull the lever when the lens is detached it does close but when it's on the camera and I click the shutter they won't close no matter what I do. Thanks.

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Thrn I agree with Karl K

Karl K said:

The camera's diaphragm actuating lever is either not working at all or too weak to actuate the lens diaphragm lever.
Look at the camera's lever while the shutter is fired. See if it moves when no lens is mounted.

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I just tried what you said and the lever in the camera works. I tried another lens on the same camera and the aperture blades close. I am sure it's the lens I think.

But you tried the lens off the camera and the blades closed. To do so one must move the corresponding lever.
As both levers worked, and seemingly you engaged them correctly, I am puzzled.

Thus, have you tried the lens in question mounted at the camera again, after you checked the camera lever working properly?