What/where is the "Coach Power switch" that you're talking about (that shows power)?
Perhaps you are referring to the Xantrex display. The other place to read system voltages is the Aladdin display unit.
There is a switch in the "row of switches" in the dash panel as you enter/exit the coach. One of these switches is for the interior 12VDC power.
That switch should have a "release button" on the switch so it can't be accidently toggled.
In the photo below you can see the switch location on a 2005 PT. The Coach power switch is next to the AC vent (in my photo I moved that switch to under the dash so I could use the original switch cutout for a different switch).
The actual solenoid that switch controls is located in the small compartment above the batteries. If that solenoid (or the switch) is bad, you can by pass it by just moving one of the larger battery cables from one side of the solenoid to the other side - so both large cables are connected together on the same terminal post.