Is there any chance that the solenoid is actually a smart relay originally configured to only charge the auxiliary battery when the truck system is charging the start battery...
There are two popular smart mode solenoids on the market that do this replacing the older generation DIODE BASED battery isolator/combiners that do not work well with smart mode DC charging voltage due to the very large DC VOLTAGE drop across the high current diodes...
These smart relays monitor the battery voltages and switches the solenoids accordingly to keep your auxiliary battery charged without discharging the start battery.
You may have defeated something with your re-wiring...
Just thinking out loud here...
We camp off the power grid alot here and one of our rules is NEVER mess with the truck start battery system including the truck alternator as this is the only way to get home haha...
We use a 2KW Generator to power up the on-board smart mode converter setup to recharge our camper battery bank back up to its 90% charge state in a quick three hour generator run time after we have discharged the battery bank to its 50% charge state.
We can do 12-14 of these 50% to 90% charge states cycles to our battery bank before doing damage to them by not having a full 100% charge state which takes a good 12 hours or so of smart mode charging..
We very seldom stay out off the power grid more that a week...
Roy Ken
