My exwife has full custody. My son is now 13 and desires to live with me.
In California can A 13yr. Old's want, need, desire, overrule a court order and
Force change in child support orders?
Thanks in advance for taking time to review request.

No, the child would be a run away, you may be changed with interfering with custody if you allowed him to stay.

You have to go back to court and file for custody, in court your child the 13 year old can tell the judge what he wants, but the judge does not have to allow it.