Electrical issues

[2400hd]

Hi everyone new to the forum although I have had many gm trucks of this era. recently began having electrical issues with a recently bought used 2007 obs 2500hd 6.0l auto Pickup after sitting a couple weeks. I started the truck up and these circuits where out. Power windows. Radio. most of the gauges other then the tach.  and The accessory lights and push button 4wd. All where functional prior of sitting. Looked at the wiring and the fuses and all looked ok. I wasn't aware if these have a master fuse of sorts mounted elsewhere then in the fuse boxes. Guessing being that all these circuits at once quiet it must be something more then the typical short in a single wire ? Thanks for any ideas to try

Edited January 25 by 2400hd

[richard wysong]

It is usually bad connections and corrosion in the underhood fuse box but also could be a bad ground, the trucks are notorious for bad grounds