Have a delta shower faucet from 2000 and the valve only goes halfway what do I need to do to fully open the valve not sure how to take it apart it's the kind that the valve handle comes apart?

Start here Delta Faucet Parts, Replacement Parts - Delta Parts @ FaucetDirect.com try to located your exact faucet or talk directly to customer service.

Not knowing the model number all I can do is put up some old.diagrams. Hope you recognize one of them. Good luck, Tom