Electrical system flickers on and off even when main isolator switch is off

[electroniclearner820327]

This is my 12 volt ONLY system in my van. Only 12 volt nothing else.

I had connected a dc-dc charger between starter battery and leisure battery and things had been working fine for a few days going on dirves but something went wrong when I was out on a longer drive yesterday.

There are two isolator switches, one between leisure battery positive and positive busbar and one between starter battery positive and the dc-dc charger. The latter I put there with the thought to isolate the two systems.

Attached an image of the system. I will mention everything is fused and isolators mentioned above but I got so fed up with the paint editor by that time I did not want to add anything else. Just know the fuses are where they should be and in working order according to the multimeter.

When I was driving yesterday I looked back at a stop point and noticed that the charger seemed to have gone off. I parked up and indeed no more lights. I got the meter out and checked fuses with continuity test and fine.

I then switched main isolator switch off and back on to see if it would jog the charger back in to action but nothing.

I then flipped both isolators off. Now...when I switched only the starter to dc charger isolator back to live the WHOLE system lights up. This has me baffled as the main isolator for the leisure battery was still off.

The dc charger will light up, where it didn't before, but so will all the stanby lights on the rest of my system so somehow the starter battery is sending power to the whole leisure system, when it shouldn't be.

The lights light up but only for a second, then go off for a couple of seconds and back on. I will note, if anyone might be thinking it, that I don't have any breakers. Only fuses and the two manual isolators.

What confused me more is last night I removed the ground in the leisure battery side, expecting that to be the cause of the problems, as that is a recent addition to the system, and still the same behavior. I also then removed the negative from starter to negative busbar and the negative from the charger to the negative busbar and STILL the same behavior.

So I am at a loss for the moment. It went dark so I stopped then and going to begin a new today removing circuits one by one until I narrow down the cause.

Can you theorize how that behavior could be happening? Some how the starter battery is partially sending charger through the whole system but I don't know how it is forming a circuit since I removed the related negatives and also the common negative busbar ground to the chasis.

As mentioned everything was working fine for days but something happened on this last, longer drive to cause this problem.

[neillnz]

I'm finding your diagram somewhat hard to follow.  There are a few conventions for drawing such things. In the case of your diagram it would be useful to not break any of the lines, it's quite ok to have them cross over each other at 90 degrees.  In the case where two lines cross over and there is meant to be a connection i.e. junction then place a solid dot there.  I do appreciate doing it in Paint would be frustrating.  Others will probably point out that there are various free online diagram tools.

Can you tell us what isolators you are using?  I wonder if one or more of them have partially failed due to not handling the DC current. 
 

[electroniclearner820327]

I'm finding your diagram somewhat hard to follow.  There are a few conventions for drawing such things. In the case of your diagram it would be useful to not break any of the lines, it's quite ok to have them cross over each other at 90 degrees.  In the case where two lines cross over and there is meant to be a connection i.e. junction then place a solid dot there.  I do appreciate doing it in Paint would be frustrating.  Others will probably point out that there are various free online diagram tools.

Can you tell us what isolators you are using?  I wonder if one or more of them have partially failed due to not handling the DC current.

I was able to figure it out. Although I already checked my own fuses I installed it was actually a fuse on the negative line on the device itself that had blown.

Good to have found it but I still don't know what caused that fuse to blow so could happen again at any time.