2002 Trident T4 cry for help.

We are currently in Scotland on Holiday and we have a problem with our Trident.
Power issues last week regarding the 12v system.
Tube light dim. When powering up the water pump everything cuts out. 
Plugged a 12v lighter socket via an adaptor into the 2 pin next to the plug. When I turn on a tube light the voltage drops from 12.8 to 8.3v. When I turn on the pump the lot goes dead, then restores to 12.8 when switched off not he panel.
Went to a camp sites and on EHU everything works as it should, pump and light.
Took it to a motorhome repairer today and got it checked out. 
Outcome.
Battery fine.
EHU is powering everything and all working fine.
Off EHU same issue but no pump draw from battery.
Diesel Heater is working fine, though it draws from the battery on a different cable.
I have replaced the three fuses under the hood and still not joy.
The chap in the repairs shop was snowed under with work but he was happy to spend 40mins but he didnt have more time to help.
We looked for more fuses but no joy.
Chap said it might be worth running a quick line from the battery to the control panel to see if it work and lay a new line, which he would have done if he had the time.

Questions.
Any opinions?
Where could any other fuses be?

Regards Bob.

Did he load test the battery or just take a voltage reading with a multimeter, I think a cell has gone down on the leisure battery

FreelanderUK wrote:Did he load test the battery or just take a voltage reading with a multimeter, I think a cell has gone down on the leisure battery

 No thats fine as he hooked up a new test battery and still the same issue.

Thanks for the reply

We have a Nuevo control panel if that helps

Roopert wrote:Do you have a solar panel?

No roopert

wRoopert wrote:Where is the leisure battery on your van?

it's under the seat drivers side

Agree with Freelander, almost everything I've read points me to a dead or dying cell in LB, easiest way is with a resistance battery tester, a multimeter will only read voltage, the resistance tester will apply a considerable load as well.

IanH wrote:Agree with Freelander, almost everything I've read points me to a dead or dying cell in LB, easiest way is with a resistance battery tester, a multimeter will only read voltage, the resistance tester will apply a considerable load as well.

two batteries attached and still the same problem

Did he actually remove the other battery before hooking up the new battery or connect them together

FreelanderUK wrote:Did he actually remove the other battery before hooking up the new battery or connect them together

Yes. Brand new battery connected.

It could then point to the pump starting to fail ,as this draws the most current when on electric and charger is working my battery volts normally show 13.4v

FreelanderUK wrote:It could then point to the pump starting to fail ,as this draws the most current when on electric and charger is working my battery volts normally show 13.4v

the pump is working fine on EHU

If it all works correctly on ehu then the wiring is ok and the 12v side is ok as your charger is putting power in to the battery ,with out ehu it’s the battery that’s powering everything, if it happens when just on battery, the battery is the problem

FreelanderUK wrote:If it all works correctly on ehu then the wiring is ok and the 12v side is ok as your charger is putting power in to the battery ,with out ehu it’s the battery that’s powering everything, if it happens when just on battery, the battery is the problem

it's had a brand new battery attached today and still the same issue

Where is the starter battery ,you didn’t get these mixed up did you

it FreelanderUK wrote:Where is the starter battery ,you didn’t get these mixed up did you

the starter battery is in the bonnet

Auto electrian time , sorry no further ideas

So all I have found is the 3 fuses and relay’s under the bonnet.
Is there any more in the van?

Picking up our 2002 Tridrnt Friday and I will try to have a look for you. Also print the wiring diagram. However as others have said it looks like a failing battery - to really test need to completely disconnect the existing battery and connect new in place - not just connect the two in parallel.

Question for anybody, if leisure battery is removed and ehu connected will the 12v side work, ie lights, pump, and 12v sockets

FreelanderUK wrote:Question for anybody, if leisure battery is removed and ehu connected will the 12v side work, ie lights, pump, and 12v sockets

It depends. Some systems need the battery in place to complete the circuit, some don't. The handbook should explain and say whether damage will be caused by getting it wrong.