I think the light meter should act the same, whether you have the lens set to A or not. I have an AE-1 at home and the AE-1 was also the first 35mm camera that I ever bought. With the lens set to A, the camera selects the aperture that was suggested by the meter, but with it set to one of the f/stops, the meter should still suggest which aperture to use - you can disregard that advice and select whatever f/stop you want, however. At least, that's how I remember it working. I could be wrong. Do a simple test. Set the lens on A and see what the meter says. Then take it off A and set it to any f/stop and point the camera at the same scene. I think the meter should still show you the same reading. If not, perhaps the meter is malfunctioning.