Think your manual will tell you that the engine heat mode is to use the AquaHot to preheat the engine before starting on a cold day. As for heating the interior using engine heat, don't turn on electric or diesel modes. Just turn your thermostat to heat. AquaHot will circulate the fluid and exchangers will heat your coach.
2006 Gulfstream Friendship G7, Cat C7 and Allison 6 spd
Honda VTX and Crusier Lift on the back
Blue Ox Aladdin, Brake Buddy, 2014 Chevy Equinox toad