You must configure the following internal settings that explicitly set the default record types of accounts in the Salesforce Developer Console:
For person accounts, Default Record Type For Person Account
For business accounts, Default Record Type For Account
Use the following sample code in the Salesforce Developer Console to configure the internal settings that set the default record type:
API_SettingsManager.updateInternalSetting('Default Record Type For Person Account|Default Record Type For Account', '<Record Type ID>');
For example, the following sample code sets the default record type for person accounts:
API_SettingsManager.updateInternalSetting('Default Record Type For Person Account', '012i000000084CgAAI');