Load shedding

[DosGatos]

Find your build date and search navistar prostar electrical circuit to download the pdf. A few ground locations. Frame rail near batteries, engine block, firewall. Check the module itself under the dash hump. Trace the heavy power leads with an ohm meter to locate possible voltage drops. Get some electrical corrosion cleaner. I use Corrosion Block but there are others. If you clean the connections at a ground post, remove and clean the eyelets. (Brass parts brush or something) Don't just squirt some product. Somewhere you'll find weak connections between the battery (+,-) and load.