Interior fusebox ignition fuses have low voltage 5.3 litre 4WD

I have been getting intermittent "check 4wd" and "service brake system" warnings for about a week and over the weekend the fan motor started working intermittently.

The fan blower motor started only working on high and none of the other settings which points to a resistor right? So I change out the resistor and still the same result so next I start taking voltage readings only to find out that every ignition powered fuse in the interior fuse box only has between 5.2 and 8.9 volts varying. I checked battery voltage and constant hot voltages on all fuses under the hood and in the interior fuse box and they all measure at 12.56 volts. I checked the ignition relay in the fuse box under the hood and both 40 amp ignition fuses. All were ok.

So my question is where do those ignition fuses in the interior fusebox get their feeds from and what could be causing this radical voltage drop? Any help here?