Is there a way I can set a limit for the max volume so my child won't turn it up all the way?

It sounds like your radio has had its hospitality mode activated. The hospitality mode is a mode which is often used by hotels or similar establishments, who wish to set a maximum volume limit on the radio. To remove this volume limiter follow the steps below.
Turn the unit on
Turn the volume down to minimum, 00, volume
Press and hold power for 10 seconds until volume numbers flash
Turn the volume back up to 50 (max volume)
Press power again to verify new max volume position

Under 'settings' there should be a 'volume limiter', when you turn the max volume up make sure press the middle button to save it

:)

Hi, No there isn't one. One suggestion is give your son some ear plugs. or sound proof the room. Good luck.

Press menu button, select settings, select playback, select volume limit, turn volume to max and press select button. This should let you play music at max volume

Some manufacturers allow you to set a max volume limit so you don't blow your ears off.  Check the users manual to see how to turn it off.
Also, have tech support install a new potentiometer for you.

you may have it at the max volume limit thing. go to settings and then change the volume settings to high

You should be able to go to your settings and and set your volume limit to a desirable limit that fits your needs. After that you should be able to raise your volume louder.

As a generic problem, check the sound volume limits in the settings menu. Some players have max limits in place and need to be adjusted for more volume.

thank you soooooo much!!!
it worked :)

You might want to try the same solution for the V-Chip (this might be the same thing as the child lock, it is worth a try) protection to see if this will help:

Changing V-Chip Settings for MV13L3, TV/VCR Combo 2001.

-Unplug your tv for 1 minute.
-Plug your tv in and turn it on.
-hold the volume down button on the tv at the same time you hold the "0" button down on the remote. This will bring up the "Set V-Chip" blue screen.
-Enter "0000" for the password and hit enter. Enter "0000" to confirm the password and hit enter.
-This will bring up the V-Chip set page. From this page you can: Turn Off the V-Chip, Change the Limits for viewing, etc.
-If you turn off the V-Chip setting, you will not have to deal with this problem again.