I completely drained the batteries overnight and then recharged them.
Will do the system drain maybe today.
With radio power being the only issue and messing with the fuse restores power I'm more inclined to think there is loose connection in the fuse box. If there was a loose connection elsewhere, messing with just the fuse wouldn't affect that.

 

A lot of the times we have seen that corrosion and loose pins on the connectors under the fuse box creates a plethora of electrical anomalies.
Carefully dismount the fuse box (IPM) and take a picture (helpful to correctly stack and reposition wiring harness upon reassembly, may not be required on RAM but, hey, film is cheap these days)
Unlock and remove each connector and inspect for any evidence of corrosion, melting, overheating, or loose pins on both the IPM side and the connector.

If you have access to the wiring diagram you can specifically look at that exact plug and pin for your 'problem circuit'
Inspect them all, repair as required, use a quality electrical contact cleaner spray, reassemble and test.

*Just because you didn't note anything that looked out of the ordinary doesn't mean that you didn't fix something. Many times in Avionics and navigation equipment, the mere act of reseating the connectors fix 87% of the problems. Test and see...

Try to resist being an 'over achiever' and adding special pookie doo like wd-40 or anti corrosion paste.... these were all available to FCM when they designed and built the vehicle, I wouldn't try to reinvent the wheel.

Cheers

** with the wiring diagram, a multimeter (or test light) and a length of jumper wire, you could test the power connection from pin x at the radio connector to pin x on the appropriate IPM harness for continuity and high resistance.

 

Agreed, what you are going to find is that the fuse box isn't wired anymore, rather all the contacts are traces on a PCB

You may find a cracked solder joint on that trace.

You could do a jumper solder splice or add a wire repair or perhaps you could retask another unused fuse slot by moving the radio power pin from one IPM connector to another...

When you get into this, pictures sure would help out the next guy who is reading this to fix his same fault.

Good Luck

Sometimes it is better to be lucky than good...

 

Disconnected battery cables from both batteries.
Cleaned all the terminals and battery posts.
Connected neg to pos cables on both batteries for 5 min (per Google)
Reconnected all cables - negative 1st.
Started truck - not only did the radio have power but so did the aux truck bed 5th wheel cam.
No raindance....

So, what does this mean?

 

So now things are working as expected?
While cleaning the battery connection is a great maintenance procedure, I suspect more likely the reboot, reset by touching the cables together has reset the FCM.
Keep an eye on it and let us know if you have more discrepancies/

 

We'll see today if it keeps working.
So my question is if the new head unit required the FCM reset and why?
Appreciate your input!

 

No, I really doubt it. The new radio does not 'communicate' with the vehicle. It just needs power and antenna (signal) (gps, sirius, or broadcast) and it was your intermittent power that was being interrupted.
Resetting or rebooting the FCM (or all the modules in this case) just gets everybody working together, communicating, once again. Why did it happen? your guess is better than anyone's.

Did you disconnect the battery while working on installing, swapping the radio? Perhaps some event gave the system a glitch.

Our old vehicles were really just on the cusp of the advent of computer controlled modules, My 2010 has three modules in the rear tailgate alone and the more these vehicles evolve, the more of this technology we are going to see.

The whole 'right to repair' lawsuit goes a lot further than farmers and their John Deere tractors. The manufacturers are squeezing out the local mechanics and forcing interaction with their dealerships. Tesla is the only one to work on Tesla... I wont be surprised when they HAVE TO go to Tesla to get tires...

 

Well, we're back to square one... no radio power. Yesterday radio power worked but 5th wheel cam didn't. Today - nothing.
Are we back to disassembly of the fuse box?

 

Nah, you need to get a voltohm meter and figure out the area where you're losing power or ground. It could be a bundle of wire that got damaged, corroded connectors in the main disconnect under dash or under the tipm... or internal circuit board corrosion in the tipm. Trace it down to the area of fault, then dig in.

 

so yes, remove the IPM (fuse box) and look under at the electrical connectors. Remove all the connectors and inspect) If you see a loose (backed out pin) or if you see corrosion, etc, take corrective action and reassemble - test.

Show pictures here. \

I use an aerosol electrical contact cleaner.]and blast the connectors, let them dry, reassemble
DeOxid is my favorite but something like CRC would work too