Removing the handgrip and replacing it or cleaning the electrical connection may be required if there is no power getting through to the camera. Battery connections oxidise over time. The following directions are for the early version of the Canon Auto Zoom.
Remove the indicated screws.
Remove the circular screw using a pointed tool and a light hammer or similar tool. By gently tapping the pointed tool, the large screw head will unscrew.
Remove the small rubber cover underneath. This exposes the last screw to remove.
Once the cover is removed the next circular screw is exposed. Use a pointed tool, as before, to remove. Also note the switch contacts are able to be inspected.
This picture indicates the small copper contact on the back of the hand grip, and the small copper strip it touches when attached to the camera. This connection relays power to the camera.
Remove the indicated screws.
Remove the screw.
This Phillips head screw is secured with glue, press extra hard to remove this screw without damaging the head.
Once the large circular screw is removed the hand grip can now be carefully lifted off the camera.
Cleaning the contacts can be done gently with the blade of a screw driver, then cleaned with a ear bud dipped in WD40. Oxidisation is common in the contact between the handgrip and camera body. If the oxidisation has occured inside the handgrip, it is easier to replace the handgrip entirely. The newer 814 handgrip can be used also.