There is an emergency start switch on the dash which activates the isolation switch joining your House batteris to your Chassis batteries. If it is defective or wired incorrectly (or the dash switch is shorted) the isolation switch is connecting your House batteries to the Chassis/Starting circuit all of the time.
When you say "unhooked", do you mean you physically disconnected the House batteries from the Isolator switch too? The isolator switch is on the other side of the Chassis battery switch (not the Chassis battery side), so turning off the Chassis battery switch does not "unhook" the House batteries from the system too.
Linear Mode
