LifePo4 and DC2DC

[WME]

New guy, first post. A bit long of a post. I've been doing solar on my RV's for many years with no problem's. As the RVs grew newer the factory chassis wiring becomes more "interesting".
I have a 2003 Winnebago Brave. 400w roof mounted solar with a 30w MPPT controller and 2ea GC-2 6v batteries. All was good for the last 5 years. The solar normally keeps the batteries charged from all the phantom load drains in the RV. This winter was a *itch, 2 ft of snow no solar output and 40 days of below 0.
Result was 2 total frozen batteries.
And now the fun begins. I bought 2 Lifepo4 100ah batteries, turns out not a direct replacement. The solar form I belong to (diysolarforum.com) has multiple posts about charging low state of charge Lifepo4 batteries direct from the alternator. So I have a Renogy 40 amp DC to DC charger hooked up and working.
Here is the problem the DC to DC input is the engine battery and the regulated output charges the Lifepo4 batteries. BUT the isolator still works.
I need the alternator to charge ONLY the engine battery. I have found the relays under the steps, but I can't find a wiring diagram.
What do I unplug, disconnect, cut, to disable house charging so that the DC to DC will be the only source for the house batteries?

 

[Isaac-1]

Since you have a DC-DC charger one simple option is to just run a new wire to it directly from the alternator and abandon the factory isolator, this is what I did on my own LiFePo4 install a couple of years ago.

 

[Mark_K5LXP]

Winnebago provides manuals and diagrams online, and yours is there.

Wiring Diagrams

Mark B.
Albuquerque, NM

 

[WME]

Thanks for the diagram link. I think I got it done, we'll see after a few trips.