Forum Discussion
Well the good news is that your solenoid test confirmed that the solenoid is working as designed and not the problem. Bad news is you still don't have an answer but you're getting close.
My guess is that the rocker switch is faulty as it is switching back off when you remove your finger from the switch. Try turning on an interior light that you can see when standing at the battery switch. If the light comes when you hold the disconnect switch on then you know what the problem is. If the RV has a stereo system in the house (not the dash mounted stereo) you can turn it on and see if it comes to life when you hold down the disconnect.
Last thing is as you say you really don't know if the solenoid is for the emergency start button. To test things like that I bought some small speakers off of Amazon. You can buy the speakers and use some wire (another use for the alligator clip test leads I linked above). Always test you equipment and hookup. For example clip the red wire on the speaker to the Battery power of the solenoid. Connect the black wire on the speaker to a ground point. If the speaker sounds off you verified you have a good test hookup. Now just move the red speaker wire over to the other large post on the solenoid. Go test the emergency start button and or the battery disconnect. One of the two buttons should make the speaker sound off and you'll now now which it is.