Does a vendor have a duty to disclose to the purchaser of an unannounced inspection?

[182 Cal.App.2d 331] '* * * When and where the action by the purchaser is based on conditions that are visible and that a personal inspection at once discloses and, when it is admitted that such personal inspection was in fact made, then manifestly it cannot be successfully contended that the purchaser relied upon any alleged misrepresentations with regard to such visible conditions. But personal inspection is no defense when and where the conditions are not visible and are known only to the seller, and 'where material facts are accessible to the vendor only and he knows them not to be within the reach of the diligent attention and observation of the vendee, the vendor is bound to disclose such facts to the vendee'. Clauser v. Taylor, 44 Cal.App.2d 453, 112 A.2d 661. * * *'