OK, time to do something back. Let's save some of your braincells.
You've reacted to my post regarding my
coach wiring. I don't know if you've read it all but I also had my doubts about some things. Your multimeter is your best friend here. It also will be a great help if you have a coach wiring diagram so you can match colors.
With or without a wiring diagram, the best place to start is your powerstation. This is the place all the power in your RV is distributed from. As most wires will disappear in the walls chances are low the previous owner changed them.
If you are not comfortable with electricity and AC and DC is combined I would advise you never to be working at your powerstation with shore power connected to avoid burning up your multimeter or blow fuses, or worse electrocute yourself.
Now, your fuses are on the powerstation and should represent DC plus. If you open it up, you will reach the wiring. If you look at the picture below you see the wiring from the fuses (1) go to connectors (2), from were the power is distributed to the different areas in your RV in different colors to identify the wiring (3), The wires from the fuses to the distribution connectors all have the same color as the wiring of your ground/minus. Of course when you don't have distribution connectors the different colors of the wires will be connected to the fuses directly.
Put your multimeter on 12V DC and put the red pole on one of the wires at the fuses and the black on one of the wires from the different color. The multimeter should now show 12.XX without a minus in front of it. If there is a minus it means that the polarity is wrong but as chances of that should be zero, let's not dig into this yet.
Write down the color of your DC+ and DC-. Next to this number your fuses from top to bottom or left to right and follow each wire from the fuse to the connector. Look at the other side of the connector tho see what color wire is on there and write that down as well.
Then switch everything that is on 12 volt on and start removing the fuses one by one. All appliance/lights connected to the fuse will go off. Write the appliance/ light after the fuse/colorwiring you wrote down before.
Now the pictures you've sent scare me because they show you have a wiring magician touching the electricity of your RV as well, without respecting colorcoding or fuses as far as I can see. First thing you need to check is if those distribution blocks are also fusible links. If not, that needs to be addressed INMEDIATELY because this is a fire hazard waiting to happen if they are not!
I think that one of three wires on the right side of the solenoid on the picture is the DC plus feed. This will mean that the solenoid is used as a kill switch to everything connected to the distribution block.
So if I were you, I would first determin were all the wires are going to, one of them should go to the coach battery. Really check were all the wires are going to.
Then you should determin what switches the solenoid. the wire for this is the purple or pink one on the small connector.
Now the next thing that I see is that the solenoid is hanging upside down. there is a wide discussion about that on the internet but thinking logically, the poles on the left and right of the solenoid should be connecting when the solenoid is on, so in my humble opinion should move up and not down so gravity or driving over bumps can connect the poles too, so in my RV the solenoid hangs straight. Better talk to somebody about it with more knowledge about them then me.
Now as the wiring seems not to be colorcoded, I don't know what your DCminus is. This you Will need to find with your multimeter.
And as last, the lighting working of and on.
Is this happening to the complete section on a specific fuse or just one light? In the last case it can also be the lightfixture itself (switch or bulbholder)
If it happens to the complete section, check if the clamps of the fuses are not too loose or the wiring behind it. It can of course also be you have a grounding problem due to corrosion.