SO the negatives are all the same density?
Are you sure the lens was not set to A? The AE1 is shutter priority. What you did sounds right..
Open the camera bak without a film in it, set the aperture to 5.6 and fire the shutter at a slowish speed - say 1/30th. Look at the size of the aperture. Now change it to f22 and fire again - make sure the aperture is changing in size....
I used to repair these cameras at Canon way back when...only thing I can think of is either a faulty lens or the aperture is on A