ISTR reading on here that there is a trick to the trickle start?
It only works when one set of batts is higher voltage or some such? So there could be a scenario it doesn't do what you want? I completely forget what that was about - except it worried me so I don't have one. Maybe a false alarm here, don't know.
Somebody will know whatever that was about----
EDIT--
Engine batt must be 1/2 volt lower than house to let any current flow from house. Says here battery disconnect must be "on" (meaning "closed"? who knows??? )
https://winnebagoind.com/resources/service/pdfs/2006-04%20Trik-L-Start.pdf