A harness connector includes a harness housing having a signal cavity and a power cavity defined by housing walls. At least one of the housing walls has a locking rail extending therefrom into the corresponding signal cavity or power cavity. Signal harness cartridges are received in the signal cavity, each holding a plurality of signal terminals. Each signal harness cartridge has a locking slot configured to receive a corresponding locking rail in a position directly behind the signal terminals to secure the signal terminals in the signal harness cartridge. A power harness cartridge is received in the power cavity that holds a plurality of power terminals. The power harness cartridge has a locking slot configured to receive a corresponding locking rail in a position directly behind the power terminals to secure the power terminals in the power harness cartridge.