Fuse F 13 chassis module, freightliner, fuel water separator heater failure

Truck had light issues and fuse for chassis module in PDM kept blowing when ignition turned on. Found melted wiring on rear tail light and replaced chassis module. Lights began working, but fuse F 13 was still popping. Traced bulkhead and chassis module connectors and pins on diagram and found the fuel water separator heater causing the chassis module fuse to pop.