My cam wont work on yahoo

Did you try different Yahoo versions? Some webcams have compatibility issues with later versions of Yahoo messenger.
Another option is to use webcam sharing software, like SplitCam.

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Its good practice to disconnect and re-connect your webcam before you start - if you have been using it elsewhere the Yahoo software may have difficulty in locating it. Mine, I just unplug it from the USB and plug it back in, if yours is integral with the computer you will have to re-start the computer, unless the software has a feature for this.
Of all the chat programs, Yahoo is the most painful software to set up but if you follow these instructions you should be ok. INTERNET CONNECTION
Webcam connected
Open messenger - on top toolbar. Left click ( > ) Messenger > Preferences > Connection - Select 'no proxies' or 'connect direct to the internet' depending on the version of messenger you have
make sure your internet connection and country are correct in the lower two boxes > Apply > OK TESTING
> Messenger > My webcam - the warning panel will launch, click 'OK' and your webcam will start. You should be rewarded at this stage with your happy smiling face. DEFAULT
With webcam still running > Messenger > Preferences > Webcam > Camera Source - set your webcam as default using dropbox. > Camera Settings - adjust settings to suit. > Apply > OK
Take a note of any additional software, if you have multiple choice for Camera Source, you may wish to uninstall any redundant webcam software later to prevent conflicts PERMISSION OPTIONS
> Messenger > Preferences > Webcam - make your selections ( who you will allow to view you) > Apply > OK IN USE
When you are both on line and wish to show your webcam > Actions > 'Invite to view my webcam'. This will launch an invitation on your contacts screen when they 'Accept' your webcam broadcast will start- There can be considerable time lag ( 1 minute) before they see you, so dont be too impatient ( You can check the status on the bottom left of your webcam panel. You can 'drag and drop' the frame to a convenient location by grabbing the top border.
There is a shortcut ( cam picture ) in the toolbar and one down by your pic as well but these do not always work
Your contacts needs to configure their connection the same as above or they may get a "webcam not connected" message If you complete the above and still have problems - check to see if your cam is compatible with Yahoo YAHOO SPECIFICATION
To find out what the requirements are for messenger webcams, check out the following.
http://help.yahoo.com/l/us/yahoo/messenger/messenger9/webcam/mstacamreq.html

Yahoo has less compatibility to webcams. But try to reinstall yahoo and then give it a try.

Thankyou