12v control panel problem Autotrail Mohican year 2000 (1 Viewer)

[David Aldred]

Hi, I have a problem with wiring and wondered if anyone has had similar.
When running off leisure battery the control panel display is dim and volts reads 5v. Battery is at 12.5v. Checked voltage at back of panel, 12v when panel unplugged, 4 volts after connecting.
Verified panel is ok by running "new" positive lead straight from battery and all ok. I then measured resistance from +ve battery connector to panel and getting 3000 ohms, i think this is where i am losing the voltage when i plug panel in.
There are 2 +ve leads in the battery compartment that join together somewhere in the van, the resistance between these is 0 ohms but from either of these two wires to the control panel is 3k ohms so i need to find out where the 2 +ve wires in the battery box join the 1 positive wire going to the control panel, because i expect a loose/dirty/faulty connection any ideas? Driving me mad. Thanks. All works ok on mains.

 

[irnbru]

@Jaws is well clued up on the wiring of Autotrails. I'm sure he will be along shortly. Welcome to fun.

 

[Ivory55]

Am not best on technology but don't some autotrail battery boxes have wiring for 2 batteries ?

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[David Aldred]

Yes i think thats why there are 2 positive and 2 ground wires in battery box even though only 1 of each being used at moment but same problem with both sets of wires

 

[Jaws]

On the later versions, both sets of wires from the batteries go to the sargent box... Where they are joined together by a busbar !!Really oddball over complex way of doing it.. On yours I believe it is even stranger as the two -ve rails are joined as you would expect but the +ve lines go to two relays where they are joined together when you start the engine so they can be charged but that is all !
You need to check the voltage of the battery with the brown and blue +ve wire as that feeds directly to the control panel
I believe it remains brown and blue.
If it is ok at the battery but not at the panel chances are it ( the wire ) has fallen foul of that most common Autotrail issue, trapped wire syndrome that has slowly worn through over the years...

I know I am proly teaching granny to suck eggs, but it is worth just slacking the battery terminal clamp, giving it a good jiggle and twist and re-tighten... It is the simple ones that catch us all out from time to time
Falling that, just cut the wire at both ends and run a new one.. It really is not worth the time and effort trying to find where the original wire has gone duff !


Addendum

I have checked and although the circuit I have SHOULD be good for Y2K models, there were some changes made.. So do a quick visual check to confirm the above info is actually relevant to your system!

 

[David Aldred]

Thanks for the info Jaws, 12v from battery is ok, its only when i plug panel in andit draws a current that the voltage drops so i think you are right with the diagnosis of a wire problem somewhere.
Excuse my ignorance but what is the sargent box and where would it be? Never heard that term before. This could be where the high resistance is.

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[Ivory55]

Thanks for the info Jaws, 12v from battery is ok, its only when i plug panel in andit draws a current that the voltage drops so i think you are right with the diagnosis of a wire problem somewhere.
Excuse my ignorance but what is the sargent box and where would it be? Never heard that term before. This could be where the high resistance is.

Sargent is the manufacturer of the panel that autotrail use.

 

[David Aldred]

Thanks, haha just realised the circuit diagram I have has Sargent written on it, what a numpty lol, thanks again.
I have asked Sargent through their technical help line where the two battery cables join up in the van , awaiting their reply.