A printhead cartridge for a printer is provided comprising a page width printhead, a media transport mechanism for transporting media past the printhead and a capping assembly for capping the printhead. The capping assembly has a movable, page width elastomeric seal, a cam connected to the seal and a drive wheel engaged with the cam. The seal is normally biased into abutment with the printhead. The drive wheel is coupled to the media transport mechanism such that, when the media transport mechanism is operated to transport media past the printhead, the drive wheel is driven so as to rotate the cam in a first direction which moves the seal away from the printhead.