Topaz t4 vw 2003 12v problem

In process of equipping van for first trip this year, on checking toilet flush pump, it was not working ,checked fuse in toilet unit it was ok. then my wife noticed the fresh water meter had stopped working, coincidence? After some time trying to make sense of AS manual (joke) gave up and started to search for clues and found one blown (slightly melted) fuse in engine compartment. The fuse is a blue (15amp ? ) replaced no change, still not working.
Fuse connectors seem in good condition all other 12v functions appear to work cooker ignition, tv supply lights etc  any suggestions !
Thank you in advance

One of the most difficult things with A/S electrical installations is that they changed the control panel make/model, and the locations and values of fuses, and just about everything else electrical, very frequently.

So unless you state what make/model of control panel you have (either by identifying it or by including a photo), it can be very difficult to advise.

A 2003 van would be too early for the first of the Sargent-based systems, so I guess it may be an MES panel?

If the blown fuse in the engine compartment was fitted by A/S then it's likely to be for either the supply to the 12V side of the fridge, or the supply to the split charge circuit that charges the leisure battery while the engine is running. You can typically figure out the function by removing the fuse and seeing what stops working, but it does require a bit of work and a methodical approach. A multimeter helps a lot too, and they can now be bought very cheaply.

Thank you for your quick reply , will start fault finding again on Sunday. sat in conservatory enjoying glass of wine at present, not good for methodical fault finding. I do have a multi meter as I was in the electronics industry for many years but I find auto electrics beyond my now limited patience, must be my age. When and if I find the fault I'll let you know.

I also think you could have an MES panel and I can tell you that the water gauges on those are very temperamental, ours certainly is. It will suddenly stop working and then suddenly start working again from one trip to the next.

I think it pre-dates both Sargent and MES

Below is a link to the vehicle handbook and below that the extracted circuit diagram.

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