Keyboard Function Keys

I had to get a new keyboard for my iMac (4 years old). New keyboard looks just like the old - aluminum with number pad. The function keys used to control volume etc. On new keyboard they only work as function keys. The box in system preferences makes no difference if it is checked or not - same issue.

Do a restart. Check if it persists.

In Library > Preferences
Move com.apple.symbolichotkeys.plist and systempreferences plist to the trash. Note this will delete any other custom preferences.
Do a restart. Check if it persists.

See if the fn button toggles the functions?

It may be a hardware fault with the keyboard.

Thanks Kaveman, Those files aren't on the list of apple.com - - - plist
Any other suggestions or am I missing something?

I'm guessing you made a typo, not apple.com - com.apple.

Strange, no com.apple.systempreferences.plist at all?

Does holding the fn key down cause them the work as expected?

You're right it was habit doing apple.com.
It goes com.apple.SoftwareUpdate.plist followed by com.apple.TimeMachine.plist

If you hold the function key they just make a noise but no action.

I'd defiantly try it on another Mac and see if the problem moves with the Keyboard, at this stage.