I also have a Luna system with the double battery monitor. So overriding takes place from the monitor. have you check fuses. should have a fuse close to crank battery and fuse close to auxiliary battery. I know it sounds silly. but I also had problems with the system once. almost spend the 100drads on the split unit. luckily found the fuse closest to crank battery blown. just changed that and it was working like nothing happened since.
Mine has got a 8min timer built in pre set. so in normal conditions it will only charge after 8min has past and all other conditions are correct. the system is pretty nonsense free. should be something small. you can reset it by totally disconnecting it from the batteries for a few minutes or so.
hope you come right
