I recently acquired a Canon QL17 GIII in fairly good shape.
It seems to be completely functional mechanically.
The battery contacts needed some cleaning so I went about it after opening the bottom plate of the camera.
The cleaning went well and I saw the battery check light glow but the needle inside the viewfinder seems to indicate an aperture 5 stops larger for the ASA and shutter speed I set. I am gauging it against the sunny 16.
I am using the hearing aid battery so the voltage is pretty close to ideal.
Is it possible that the meter is functional but hugely offset? I haven't run a role through it with the meter yet. Should I?
When CDS cells lose sensitivity, the meter will overexpose, it's the common failure mode.
I'm pretty sure this camera uses the "trapped needle" system of shutter priority automation as the earlier Canonets did - this means that if the needle indicates the wrong exposure, wrong exposure is what you'll get, unfortunately.
Try this: move the film speed ring from end to end a couple of times, and then test the meter at a few settings to see if the readings change accordingly.
What Brian said, I forgot that. It's also possible that an internal calibration potentiometer has oxydised contacts, this can be cured by moving the wiper back and forth, returning it to the original setting of course.
The shutter sounds ok.
I marched the ASA ring up and down about half a dozen time.
Now it is over exposing by about 3 stops I think.
I might just have to use it on only manual after all...