My ex has not paid his court ordered child support in a year. I have a writ of
Execution from the court, but have no idea where he banks. When in the state of California can I have him arrested for non payment, it has run into the thousands.

You won't likely get him arrested. In California they do just about everything short of that. First, you'd have to get them to file contempt (he has to be at least three months behind). If they have no job on record for him the DCSS won't even take it into court because as they say "we have no income to get a wage garnishment on and the judge won't hear it". Can't tell you how many times I've heard that. They will tell you that they will suspend his drivers and any business licenses (oooo big deal right), that it has gone on his credit report (again big deal), and that they will intercept any Federal and State tax returns and put a lien on any personal property. All of which will do absolutely NO good in enticing him to pay. The only way you will get a warrant for him is if you get a private lawyer and file contempt for non-payment. Sorry to say all that but unfortunately I speak from experience.