Air conditioning for purposes of cooling a unit is an amenity rather than a legal requirement (i.e. a functioning heating unit). If the unit was advertised as having air conditioning then the lack of working air conditioning would be a breach of the rental agreement but I would not use this to justify non-payment of rent. Review the attached link.
This is not a substitute for a consultation with a housing law attorney in your community.
Though I agree with my colleagues that there is no requirement in CA that a landlord be required to provide AC (though heat is required) some Counties or Cities may require it as a local ordinance. As I do not regularly practice in SB, I am not familiar with those specific local laws.
To be sure, I would contact a local landlord-tenant lawyer to determine what your rights - if any - actually are.
Adam Jaffe Law Office of Adam Jay Jaffe 124 Lomas Santa Fe Dr, #204 Solana Beach, CA 92075 (619) 810-7964 www.smallclaimsappeals.com Adam@AdamJayJaffe.com This posting is provided for “information purposes” only and should not be relied upon as "legal advice". Nothing transmitted from this posting constitutes the establishment of an attorney-client relationship. Applicability of the legal principles discussed here may differ substantially in individual situations or in different states.