[Richard]

This is Richard’s rendition of how I think it is supposed to work. Others may have a different perspective, and I will sort of revisit what both Michael and Jack said.

The merge solenoid in my opinion should only be used for emergency starting of the coach OR carefully monitored charging of the house batteries by the engine. Use a 200 AMP continuous duty in this application. Some coaches have a two trigger wires, and some coach have one. The purpose of the two position switch on the dash console is to provide power from either chassis or house to close the solenoid.

Leaving the batteries merged is a recipe for a totally dead coach. I am aware that Newell advises otherwise.

You “should” have an echo style charger that uses current from the house battery/inverter charger to keep the chassis batteries topped off. Look underneath a carpet covered box high up on the wall in the driver side inverter bay. A word of caution for those who have installed Lithium banks. The lower float voltage of the Lithium charge profile will result in the echo charger NOT keeping the chassis batts topped off since the echo charger works off a differential voltage between the two. For example if you are floating the lithiums at 13.5, then the echo charger will charge the chassis batteries to somewhere between 13.0 and 13.3, not a full state for a lead acid.

Yep, passenger footwell for that fuse. There may be two, depending on how the coach was wired with one or two trigger wires.

Lastly, you will find two similar solenoids in the engine compartment. One is the merge solenoid, the other is the starter relay solenoid. There are not intended to be interchangeable but in a pinch it is possible. The starter relay solenoid is an intermittent use coil. Using it for the merge solenoid will result in a very short life. I carry spares of each in my spares box. I have also traced a merge activation problem to a faulty switch on the dash. Just sayin……..