In program mode, the aperture needs to be set to minimum for the meter to set proper shutter/aperture combo. Auto mode is aperture priority and sets shutter speed accordingly. Manual/spot mode displays a bar graph with += symbols for over/under exposure warning. There is a single photo cell facing toward the film plane, and only takes (partial) reading from light passing through the mirror, and actual reading is accomplished from direct reading of light reflected from film.
My suggestion is to test the camera with film and printing the results ascertain if it functions properly.