It depends.  If the check or letter attached to it says anywhere that it is a full refund, then don't cash it.  That could act as an accord and satisfaction, whereby you agree that amount satisfies your claim.  You are more protected if you don't cash it.Call him and dispute the charges.  Be reasonable.  If he is being unreasonable point his way to California Civil Code Section 1950.5(L).  You should sue in small claims court for your deposit multiplied by two plus costs and interest.  This is what Section 1950.5(l) says: (l) The bad faith claim or retention by a landlord or the landlord's successors in interest of the security or any portion thereof inviolation of this section, or the bad faith demand of replacementsecurity in violation of subdivision (j), may subject the landlord orthe landlord's successors in interest to statutory damages of up totwice the amount of the security, in addition to actual damages. Thecourt may award damages for bad faith whenever the facts warrant thataward, regardless of whether the injured party has specificallyrequested relief. In any action under this section, the landlord orthe landlord's successors in interest shall have the burden of proofas to the reasonableness of the amounts claimed or the authoritypursuant to this section to demand additional security deposits.