Hi Koi, you are not alone.
I'll get you started and electricians better than me will be along.
First, is your multimeter a digital or dial reading? Some meters are sensitive to phantom readings so those 18v readings may not really be there.
I can see two cables entering the bottom of that box and I know there are more. Make a list of all cables you see coming in and the number of conductors and color. Put that list into a vertical column on the left side of a sheet of paper.
Now make a list of all devices being powered from those switches, again a vertical list but on the right side now.
Leave out the bare copper and label the wires you know and with pencil draw a connection between switches and devices.
As you fill in the connections it usually becomes obvious where other wires need to be connected.
May seem like a silly exercise but it dos help to unscramble the birds nest we are seeing.
Pros will be along.
Bud
I'll get you started and electricians better than me will be along.
First, is your multimeter a digital or dial reading? Some meters are sensitive to phantom readings so those 18v readings may not really be there.
I can see two cables entering the bottom of that box and I know there are more. Make a list of all cables you see coming in and the number of conductors and color. Put that list into a vertical column on the left side of a sheet of paper.
Now make a list of all devices being powered from those switches, again a vertical list but on the right side now.
Leave out the bare copper and label the wires you know and with pencil draw a connection between switches and devices.
As you fill in the connections it usually becomes obvious where other wires need to be connected.
May seem like a silly exercise but it dos help to unscramble the birds nest we are seeing.
Pros will be along.
Bud