Just cooking dinner tonight, when the lights [12v] went out, came back on for a second then went off, on investigation the fuse above the light fuse [taps] was melted and the light fuse very hot, took out the tap fuse and put a new fuse in the lights even though it looked OK, it started smoking, as far as I can tell nothing 12v is working, still coming home in 3 days so not too bad.
Dave

That's bad news. I would consider disconnecting the battery until you can find out what is wrong, and maybe take out the mains unless you can isolate the battery charger. Sounds as if you may have a short somewhere. Hope you get home without any more trouble.

Check the low voltage output from the BIP.....this could be higher than normal. On mine I found output was about 17v.....too high,, so I disconnected the transformer and installed a separate intelligent battery charger retaining the BIP as a connection board only. I gather that this is a common issue.
Alternatively, it could be a short somewhere in your wiring.
Time to get the multimeter out!

I had the same fault on my 530 GT. Sandy at Jandi traced it to the wiring for the front dinette overhead light shorting between the metal framework and body. Fault rectified by rewiring the light fitting.

Its got worse, the 12v fuse didn't blow, just the plastic melted and smoke came out so I pulled all the 12v fuses, next night we tripped the site bollard and the van at the same time, when we reset them the fuse box started smoking, so off with all power had to bring power in through the toilet door and up the pan on a 4 gang extension lead, [we don't use] the toilet it was enough for a heater and light. time I think to get an expert in, maybe get a new unit installed [by the way we don't have or want a battery] as we aren't booked to go anywhere till next March we have some time to find someone good, any suggestions? have car will travel.
Dave

Sounds like the BIP unit has failed.....not uncommon. Do a search on this site for threads......basically you need to replace the transformer with a new power unit or I did find a chap who could rebuild the BIP although this was not really cost effective.......

I found my BIP had started giving out 17v and I had to do something before I had problems like you!

I’m not recommending the following, but maybe it is what you might be looking at installing https://www.thecaravanshop.co.uk/chargin.../prod_1069.html

You may be able to retain the existing BIP as a fuse board providing that you have not cooked any of the installation. This is what I have done.