Help a numpty please

[tight fart]

I'm replacing the radio in my camper, the old radio would work on either the 12v supply when the ignition was on, or the leisure battery 12v supply if that was switched on.
The problem I have is I can get everything to work as it should but when I'm on the 12v from the leisure batteries it's putting 12v back into the van circuit powering up the dash lights!

Any ideas how I stop that?

[tight fart]

I'm going with 2 10amp diodes one on each feed, what could go wrong?

[tight fart]

Ignition lights etc

[tight fart]

No aux position on key.
I don't have any diodes yet, just trying to stop feed no 2 reverse powering feed 1.
If that makes sense?

[tight fart]

Yes thanks for that, i am hoping to get it working as it should not with a switch, if all else fails ill go the switch route, for now ive ordered a couple of 10amp diodes and will try that first.

[tight fart]

2 reasons, first is there will not be a permanent drain on the leisure battery as it's only on when when in use, most of that time is also on EHU so it's also being charged.
2nd I asked someone else and they advised a different solution.

[tight fart]

Thanks, change over relay sounds good, I'll order one and have a play.

[tight fart]

So would one of these work?
And I'm guessing 85-86 live & earth,
30 feed to the radio
87 feed from ignition
87a feed from leisure battery?

[tight fart]

Are you sure it's not 87 from ignition?

[tight fart]

I've confused myself here as I only have 2 power feeds, both switched
1 from the ignition that is currently powering the radio
And the 2nd from the leisure battery that I switch on when required when the ignition is off.
Do I add a third permanent power feed?

[tight fart]

Thanks so much for your help, you got me there in the end, all working as required. Cheers.