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Motorhome Electrics

Transit Mk6 & Mk7 Forum. All Transits 2000 - 2013

Motorhome Electrics

Postby dave 418 » Tue Jul 17, 2018 11:41 am

I have a motorhome based on a 55 plate 350 Mk6 Transit. On our last trip out the fridge would not work on the 12volt setting when moving between sites. I have found the fault to be with the fridge relay under the drivers seat. It has a permenent 12volt feed but no earth or trigger for the relay. Checking the wiring I have found the earth and trigger wires are tapped into the wiring for a large relay wedged down the side of the batteries. There is a small two pin plug and two large red cables that go to either batteries. The fridge relay wiring is spliced into the wires before the small plug.
Any ideas what this relay is for?. I could bypass these connections but I would like to know what this really is for first. Any ideas please. Considering how much this motorhome cost new I find the wiring under the drivers seat very amature and a mess.
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Re: Motorhome Eletrics

Postby chris72a » Tue Jul 17, 2018 4:51 pm

As far as I know a relay is there to convert a high current to a lower current with it removed it may blow your fridge, are the batteries connected if so you should be able to re-wire the relay just to one battery and neaten it up a bit. Im no expert and have only just been researching relays as I need to install one for my spotlights.

Cheers
Chris.
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Re: Motorhome Eletrics

Postby dave 418 » Tue Jul 17, 2018 6:01 pm

Hi Chris, I have been back out to do further checks. I think the relay at the side of the batteries is in some way connected to the battery charging. Our older motor caravan was easier to understand, there were two relays fastened to the battery tray. One for the fridge and one for split charging the laid urge battery. As fitted by Ford from new the 350Transit had a main and secondary battery under the drivers seat. The motorhome converters replaced the secondary battery with a leisure battery.
The small two pin plug on the large relay has no feed or earth to it even with the engine running. This is were the fridge relay takes its earth and trigger feed from.
The simple fix is to re-wire the fridge relay but that still leaves the original fault at the plug. This may involve a wiring diagram to resolve.
Hopefully some one out there will give some ideas to solve this history.
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Re: Motorhome Eletrics

Postby jimbo07g41 » Tue Jul 17, 2018 7:18 pm

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Re: Motorhome Eletrics

Postby dave 418 » Tue Jul 17, 2018 10:05 pm

I have proved the fridge works on 12volts when I by-pass the relay. My problem is Transit related, once I get my computer sorted I will try and download a wiring diagram. The screen on my I-Pad is a bit small. I have four weeks before our next outing so hopefully something can be sorted.
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Re: Motorhome Eletrics

Postby dave 418 » Sat Jul 21, 2018 7:25 am

I have done some further checks and found the main vehicle battery is charging at 14 volts but the front battery voltage dosnt go up with the engine running. The large relay
is the charge relay and the fridge wiring is spliced into the small plug under the relay on these motorhomes .
As the alternator is charging my next move is to trace the wiring for this relay. A wiring diagram for an 03 built 350 Transit,rear wheel drive, 2.4 diesel is what I need. The confusion comes that it is 55 plate but the build year is 03. Any further help please.
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Re: Motorhome Eletrics

Postby dave 418 » Thu Aug 02, 2018 11:48 am

I now have a wiring diagram for a Transit twin battery charging system but it dosnt mention the large relay next to the batteries or the wiring from it. I know the alternator is charging the batteries so I assume Relay 5 and its wiring is ok but there is a further Relay 15, Battery saver Relay.
Can any one shed any light on this problem or suggest were to find a wiring diagram, maybe mine being a 350 its wired differently. As all the parts are marked with Ford part numbers this is as built not an add on by the motorhome converters. The nearest I got to this was the American Ford Ranger wiring.
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Re: Motorhome Eletrics

Postby dave 418 » Sat Aug 04, 2018 4:35 pm

I have replaced Relay 15, the Batery Saver Relay. Fault still there. I spoke to some one that works at our local Ford Truck and Van dealers and he thought it must be a special build because that year Transit 350 single rear wheel didnt have twin batteries. :!:
I can run my fridge on 12 volts between sites so that will do until any clues are forthcoming.
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Re: Motorhome Electrics

Postby the dutch guy » Mon Aug 06, 2018 7:40 am

why not just pull the whole deal out and mount your own stuff?

rip the whole lot between the starter and aux out and put one of these in:

https://www.ebay.com/itm/ATV-UTV-Dual-S ... 46561378df

main advantage is that if you charge from the motorhome side with solar or external power you also keep the starter battery charged. ift he battery voltage is above 12.8 like when you have a solar panel connected it will connect both batteries and you also start using both batteries and increasing their life.
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Re: Motorhome Electrics

Postby dave 418 » Mon Aug 06, 2018 7:59 am

That would be one solution but all I need is the right wiring diagram and I am sure this could be resolved. As I said things were a lot easier on our Mk5 Transit apart from the never ending rust.
Being a well built motorhome I cant even get the cab carpets up to follow the wiring loom. There are the Ford rubber mats with carpet on top that is very well fitted. If I knew were to look after the battery box I might be able to trace the wiring to its source.
Never mind there must be worse things out there than my fridge and battery wiring.
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Re: Motorhome Electrics

Postby the dutch guy » Mon Aug 06, 2018 8:04 am

the only place you could possibly get the right one would be the folk that built the motorhome part. they did the conversion so they have done the mods to the electrics.
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Re: Motorhome Electrics

Postby dave 418 » Mon Aug 06, 2018 1:13 pm

I have spoken to the motorhome converters about this problem today. This model of motorhome was a small batch special build and they couldnt remember any thing special about the wiring. There usual policy is to not disturb the base vehicle wiring. The fridge relay trigger and earth were taken off the nearest ignition live and neutral to were the motorhome fuses could be fitted. In my case this was the two wires coming into the large relay in the battery box.
I have found wiring behind the o/s wheel arch trim but need to move the van to check this properly due to being parked against a hedge. A thought for another day is to
check wiring colours. At the moment my back is not too flexible for contortions under dash boards. :(
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Re: Motorhome Electrics

Postby dave 418 » Sat Aug 11, 2018 3:30 pm

:D At last I have sorted the fridge wiring issues. :D
I had one of those what if moments thinking is the large relay between the batteries is connected to the charging and is the earth switched as per the rest of the charging system. With the engine running the relay is switched via its earth. The other wire from this relay was split in two one not being connected to anything.
The 12volt motorhome wiring is behind the rear battery, Representing a rats nest of odd coloured wires one had a battery live and a fuse. The wiring to this fuse is red, then its green and yellow after the fuse. Connecting this wire to the green and yellow in the relay wiring and starting the engine the fridge now works on 12volt. At some time on the last trip away this wire must have disconnected from this fuse. :roll: . I can only think that this relay disconnects the main battery after starting.
The motorhome wiring will get a good dig out next. I may remove it and start fresh with a proper junction box instead of stuffing loose wires down the back of batteries.
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