Trailer Electrics - Fuses (2019 Van)

[Paperstone]

Hello everyone, the questions that I’m looking for help with are;
- what fuse my 7-pin trailer pin should be running off?
- where the trailer electrics should ideally be wired to?  
- Is it reasonable to have wired the trailer into a 3 amp fuse?
- Is it reasonable for me to ask for towbar installer to re-wire it into permanent live as AA suggested?
Full disclosure, I’m only just now reading up on Van electrics, and new to this forum so please forgive obvious errors/misunderstandings and let me know if I’ve posted in wrong section 
Any feedback/advice appreciated.

Fuller Background to questions for anyone interested;
- I had a tow bar with 7-pin electronics installed by local reputable shop 
- verified before leaving that the electrics worked when attached to their light board.
- Picked up a lightweight unbraked 7-pin trailer, plugged in electrics, and practiced in their yard, all good.
- About to leave the yard, everything now turned full on in cab for long journey, satnav, music, phone charging etc etc, I added in brakes & indicator & Van just shut off 
- AA diagnosed the problem as a blown fuse.  On inspection, said that ;
“Patrol found the following fault code/s:System : Engine control 1 - 8HN / Engine management EDC 17C 60P0123 - Intake air flap position sensor. Error Message : Voltage too high.Found fuse for dash blown. Fuse had been piggy backed to supply trailer lights. Replaced fuse van now runs. Re wire trailer lights into a permanent live so customer can continue journey - Will require re wiring when at home”

I’m now at home and trying to work out next steps - I’m assuming the Towbar installers used fuse F19 as the fuse table for the 2019 states that F19 is for the Trailer Interface Unit, but also says Rating (A) 3.
The van is Berlingo 2019, ENTERPRISE M Blue HDIi

[evdama]

I always take a dedicated live feed and install my own inline fuse (and a full relay taken off the rear lights)
The modern cars electrical system is complex and fragile - best left well alone.
In addition yours is Chinese made and French designed - even more reason.
A three amp fuse at 12v with all bulbs lit will be at its limit without extra load from the van itself.
Hobson's choice to take it back to the goons who wired it or give them a wide berth.
They'd showed you it worked before you left so that would probably be their defence so get a print of that AA report ready

[Paperstone]

thanks for this - good advice, and hopefully a straightforward conversation with the installer will sort it out - I get their thinking, but definitely optimistic in terms of load!

[uk_friendly_fire]

Get a dedicated wiring harness fitted. With this canbus system it's the best way to avoid faults. I got my detachable Westafalia towbar fitted at a Witter dealer.

A separate fused wire was added from fuse box to 13 pin socket.

The ECU was programmed to recognised trailer connection as this activates trailer stability control and deactivates lane departure warning. Stability Control applies automatic differential braking to smooth out snaking should it occur

Expensive but absolutely no problems at all 3 years on. Towed caravans, trailers, bike carriers, and MOT tested. Peace of mind costs

[Paperstone]

Cheers, I’ve just talked to original fitter, and they’ve already said sounds like it was a mistake, and happy to sort out - I’ll ask them about dedicated wiring harness option - and if not now, can be my back up plan in case of future problems!

[Romahomepete]

I dont know if K9s are the same but on both the M59 and B9 versions there is a thick white wire behind the passenger side boot panel. This becomes live when you fit the correct maxi fuse to the lower fuse box in the engine compartment

Peter

[Paperstone]

Update in case anyone finds it helpful
- the installer didn’t wire it into a 3A fuse, but used a piggyback add-a-circuit blade fuse holder, which should mean the original 3A circuit is unchanged, and the new trailer 15A circuit runs independently.
- They think failure may have been the component, and also decided not best using 3A and 15A in same unit.
- They’ve rewired it using a fresh piggyback add-a-circuit blade fuse holder, and into a different fuse (F29, 20A, which according to the manual I got  from ScanMyCitroen app is Audio system, touch screen).
- Checked on-site by running everything we could think off at full tilt, including light board, no failure, drove home fine.
- I still need to do final belt & braces check by hooking up to actual trailer, but won’t be for a week or two

Any further issues and I’ll go with the suggestions earlier to use white wire/direct feed, but for now, am running again, and I haven’t had to touch it myself, so happy.

[uk_friendly_fire]

Just looked up my "Right Connection" wiring instructions. F10 was piggy-backed with a 20amp fuse