A fuel heater module and a water-in-fuel sensor module are disclosed that are configured to be connected to an outside surface of a filter assembly. The fuel heater module includes an inlet port and an outlet port with a heating element positioned in the fluid path between the inlet and outlet. A thermostat is included for controlling operation of the heating element. The water-in-fuel sensor module is configured to detect water in the filter housing that it may be drained from the filter housing. Both modules are configured to be attached to an outside surface of the filter housing thereby being readily replaceable.