Oh the other NO CRANK issues I've had (And one no start)
The no start was post a major job turned out to be a bad connection took less than a minute to fix.
THe Did nto crank
I turned the key and I heard a CLICK, not a CLUNK but a CLICK (different musical note) Now I know the starter circuit on this RV has both a SOLENOID on the starter (Goes CLUNK) and a pilot relay in the fuse panel (CLICK) yup. dirty contacts. Removed, opened, cleaned, replaced, Varoomed.
THe not entirely amazing thing is that Sitting in the driver's seat using nothing more than the ignition key and my Ears. I correctly diagnosed it.
I guess those electronic classes I took just about paid for themselves (Back then Tuition was only a bout 100/class I took 4 classes)