That's a really good place to start for understanding some of the "weirdness" we get in RV! It is also one of the more frequent causes of trouble for different reasons.
Since we talk it so much, I know it pretty well, so I can give an overview.
One frequent problem on forums is we miss some details on which RV and there can be some details different on different floorplans. I looked at three different models of this one and they all seems to show a mode solenoid, rather than the later solid state BIM system.
For less trouble the BIM is better but for ease of spotting and repair, I like the solenoid. Solid stat hides lots of things I like to see?
Contacts on it close/open every time we start the engine so arcing can be a trouble cause! But also easier to figure and cheaper to replace!
To "decode" Id on wires or from drawings use this chart as it gives "from" and "to" of wires as help to figure what they do:
https://www.winnebago.com/Files/Files/Winnebago/Resources/Diagram/electrical_guide.pdf
Click this snip of the drawings to see better or go direct here:
https://www.winnebago.com/Files/Files/Winnebago/Resources/Diagram/Wiring.htm
Go to chassis electrical box for this info. but lots of other sections for different parts!
Mode solenoid is controlled by wire LR from front. It goes hot when we push a dash switch labeled different on different RV. Boost, Aux, etc. are some names but a momentary switch which lets us do a "jump start" by pushing the switch while we crank if we have a weak chassis battery. Jump start without jumper cables!
OR this LR goes hot from a point called ignition hot when we are driving!
This LR sends power to coil of solenoid and through it to ground. Ground is found at the mounting screw but doubled with FM going to ground!
This closes contacts to connect chassis battery on left big lug (red?) to coach (green?)on right!
This is possibly the problem when not charging as we drive. But while here, some other info may help?
The coach battery goes a short distance to the coach battery disconnect relay.
Tape was on ends but tends to fall off!
Battery cables ID :
The switch near door(?) operates to engage or disengage this latching relay. The relay stays in last position by magnet after we let go of the momentary switch! We don't use battery to hold it full time!
The biggie to know is that much of the battery drain is removed by the relay but some comes off BEFORE the disconnect. That means we can't store the RV with the disconnect turned off and assume the battery won't go dead after a month of two. Stay alert to avoid killing batteries! This relay is not involved with the charging, though!
Back to testing why no charge as we drive?
When we turn the key or push the boost/aux/?? switch, we can often hear this solenoid "clunk" as it is heavy duty!
So we need it to move but then the contacts may be corroded and not pass the power on?
If not moving, make sure voltage is getting down to the wire LR and the FM is giving good ground! Shorting from a big lug to the small center lug should also make the solenoid jump to assure the coil is good!
One quickie to test without having to get to the solenoid is watching the coach battery voltage as we push the switch or start the motor. The voltage at coach should follow the revving of the engine if they are connected together! If coach battery voltage is not changing, look back toward the solenoid!
There are some which have a "mega fuse" inline between solenoid and batteries and it can hide or have dirty connections. Corrosion is a major thing on Rv that set for long periods between use!
