First, to make sure that poor contact is not causing the issue, since you are positive that the batteries start out good. Remove them from the camera and clean the metal battery contacts inside of the battery compartment
and on the battery with a q-tip and alcohol. The connection is very critical and a very small amount of residue or dust can inhibit the power transfer. Also, check how well the battery door shuts and if necessary adjust the metal contacts by gently prying them with a small screw driver to increase the tension.
It is a known issue that as Powershot cameras that use only 2 AA size batteries, tend to require a little more power as they age due to deteriorating parts and surface residue. Lens movement uses the most power. That is why the connection is so critical The only suggestion that I have is to try a set of high power lithium AA batteries. They have a higher, more steady, power output. This has solved this issue about 60% of the time,
Even if the lens appears to extend correctly and only fails intermittently, it is quite possible that it does not make it to the correct sensor point periodically due to an obstruction like a grain of sand or residue build up. A lens position error will halt the camera start up process. Lens errors are a common problem. Dirt can get into the gears or the lens can become misaligned from being carried in pockets, purses or at the beach. The two suggestions below may resolve the issue.
Try compressed air. With a fine tip can of dry compressed air (not a blow dryer) set the tip between the lens turret and the camera body and turn on the air while moving the tip around the lens. It should remove all dust and sand. Turn the camera on and it should function fine. If not, you can try the fixes below.
With newer cameras I am usually hesitant to suggest these options since they include some more extreme procedures that may cause further damage if not done correctly, but since your camera is older, they may save you an expensive repair bill. The links below give step by step DIY instructions on troubleshooting and attempting to fix this problem. The lens structure of these compact cameras is the same so the examples do apply to this unit. These procedures are effective about 60% of the time. Click on or copy and paste the links into your browser.
LENS FIX 1
LENS FIX 2
If the "do it yourself" approach doesn't work out for you and you need conventional repair suggestions please let me know.
Please keep in mind that my diagnosis & solutions provided are directly dependent on the accuracy of your description of the problem. As with any "do it yourself" fixes, success is a "team effort", since I can't see or touch the camera, and relies on the customer's manual dexterity and ability to follow the instructions well.
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