Build in flash not working
If you found your internal flash not working just after you removed the external flash, this tip may help you solve the problem.
There is a switch on the hot shoe, which detects if an external flash is attached. The switch is pressed down when the external is attached. The camera will bypass internal flash.
If the switch is obstructed by dirt, it won’t pop up after the external flash is removed. In this case, the internal flash won’t fire because the camera ‘thinks’ the external flash still on the hot shoe.
Figure 1 shows you how to remove the plate. Use a small flat screwdriver to lift up the plate a little and slide to take off the plate.
(click on pictures to enlarge)
Now you can see the little switch clearly. Blow compressed air and press the switch several times, clean out the dirt properly.
If it doesn’t work after cleaning, you may need to go further to take the camera apart to check the switch inside.
Different modes have different structures. Figure 3 shows the point you need to check on a Canon PowerShot G9. Clean the contact surface and adjust spring strip if necessary. This tip just gives you an idea where to check.
I did fix the problem by taking out the battery overnight and letting the power drain. The camera then came back on and the built in flash worked just fine.