Hi
I found my problem today. It turned out to be a faulty vacuum solenoid that always kept my front axle from engaging. Thank you for the guidance with the troubleshooting. cheers

 

Does this mean the 4x4 works ?

The top side will always have +12 v DC to it. The switching is done via ground.

Nope, just like AC, voltage drop is over the device.
Think of it this way, if you have a AC light bulb, and measure from hot to Neutral, what does the meter show ? 115 V ( or 120, or what ever the actual voltage is peak to peak, halfed and * 0.707 or RMS ).
Voltage drop is still the same over a single series device.

Fuse #20 in the EVTM says for manual trans only. No note as to if it does something else in an auto trans, so I would say fuse #20 is not needed. Don't know if you missed that in post #10 above.
https://www.f150online.com/forums/3570452-post10.html

 

Oh crap, sorry I was replying to your previous post when you did this. please ignore that one then.

Glad you found the problem, and it was an easy mechanical problem, not a GEM issue.

Any time, that is why we are all here.

Too bad, I thought we were going to have a post count higher then Brad with adding electrical devices

 

FYI

That 5A fuse in the mini-box of the 97 and 98 trucks is the PCM KAM circuit. It doesn't run the PCM, it just supplies power the non-volatile memory in the PCM.

That's the fuse to pull to reset the PCM's memory so you don't have to disconnect the battery (and reset your clock and radio).

Steve