Caravan 12 volt what should happen?

[ericmark]

There is a relay/fuse box with 5 relays and 14 fuses even spread and 12 names even spread so names are useless. One relay seems to do water pump, one main isolator, one switches from caravan to car battery when car plugged in and it seems two switch over when car ignition is switched on.

One fuse is only live when car plugged in, and the one labelled ignition seems to work lights. I found two in line fuses by passing the fuse box so the master switch did nothing, and the lights did not swap between car and caravan supply, plus the caravan battery was not charged and only worked motor mover, all caravan electrics came direct from charger.

I think I have cured most faults, however since not sure what should happen, hard to know, it seems crazy that there are 4 light switches at the door, but you have to walk into the caravan to switch on master switch before they work.

Caravan one of the Explorer Group Tourers (Elddis) called Odyssey around 2004 the printed circuit for fuse box marked PCB-147-MD and it looks like this.

Any idea what should happen, then I can see if it does happen, I have started working out what things do this is it so far.

I also have a problem with radio every time the supply is dropped either master switch or plugging in car radio goes into demo mode and auto switches on, there is only one feed to radio, clearly there should be two. So looking for ideas small battery or capacitor at radio to hold supply so it does not go into demo mode.

Any ideas welcome.

 

[john4703]

As I see it there are 12 fuse (plus two empty fuse carriers) and 12 labels. If the fuses and labels are in the correct order the labels seem to be suitable for the fuse rating. 5A for the heater and water heater as it is only a control circuit and not heating. I'd guess that ignition would be the spark ignition for gas cooker and water heater and possible space heater although any of these could have a separate AA battery for spark ignition.
A lot of caravans have a master switch that cuts off all 12v power so that when it is left for a few weeks, or months, the battery does not discharge. Once it is on it should stay on until you turn it off.

This site is really helpful for all caravan issues and there is probably a member on there with the same caravan as you
https://www.ukcampsite.co.uk/chatter/display_forum_topics.asp?ForumID=31

 

[ban-all-sheds]

As I see it there are 12 fuse (plus two empty fuse carriers) and 12 labels.

There must be some fuses stuffed into gaps between properly installed ones.
As you say, there are 12 labels on the right, and 12 ratings on the left, and there is a gap in the fuses. But I can definitely count 12 fuses....

 

[ericmark]

Sorry there were two fuses removed in photo, to date I have worked out from picture diagram to right. Note not all 10 Amp fuses the colours show amps, I have three fuses where I can only guess, one of the top three are unused, what I am trying to work out is what should happen when the 7 pin S type socket to car is plugged in? Top two relays are pulled in with car ignition supply, next one with car non ignition supply. I will guess one of the top two relays will connect the non ignition supply to battery? The third relay down disconnects lights from caravan battery and connects them to car battery.

However there are two ignition relays and I can't work out why, at first I thought maybe fridge, however simply can't see why you would relay fridge supply unless it has an under voltage drop out, and with no electronic components that is not really going to happen. I would guess fuse 4 is fridge it does not connect to any relay. I would guess fuse 2 is battery charger. Fuse 5 likely non ignition supply from car. However this puts them in wrong order to cover.
Van Batt + is Van Batt + I connected it.
Fridge is likely Battery charger.
Unused
Car is likely Fridge
Unlabelled likely Car
So why two relays which I know activate with car ignition supply? one I can understand two I can't work out. The main point of exercise is at the moment there is no connected S socket on car, so those 3 relays have never done anything, I have only powered them with a 7 Ah battery to test them. What I don't want is to find with new tow car the car and caravan battery are connected when starter is cranked, or the fridge continues to work when engine is off, or plugging in latches relays which means fridge will discharge caravan battery when unplugged.

As bought there were two in-line fuses, clearly added due to uncorrected faults, this resulted in the master switch doing nothing. I found a blown fuse which was next to label ignitions which enabled one in line fuse to be removed, removing second one resulted in caravan battery being completely disconnected caravan ran of the charger. I threaded the wire from battery into fuse/relay box and connected to top spade and all now seems to work in caravan without car connected.

What I need to do is work out how to test is actually does what it should, but until I know what it should do, that's not easy. I goggled the relay board and it seems it has now been superseded, I can find the new one for sale and a chart telling one how to change wiring, but unless I know wiring is correct to start with that does not help.

I found wiring diagrams of caravan, however colours don't match and it shows 4 relays not 5. What I don't want is when we get new tow car and connect up for the 15A fuse to caravan battery to blow as we start car engine, or for car battery to become discharged. And if I decide to fit a DC to DC battery charger in caravan I need to know were to connect it.

With modern cars and caravans there is a whole new method of connecting, as the modern car does not simply float charge the car battery, the charging is connected to engine management and only charges on over run or when battery below a pre-set limit. So all the old split charging relays and diodes are redundant, DC to DC inverters is how it is done now, and since monitoring caravan battery voltage they should be in caravan not car which is all new and only started in last 5 years or so. To be frank not really worried about charging caravan battery from car. But I do want fridge. I don't drive for long enough to ever put enough in caravan battery to be worth the expense. But still don't want car to be using caravan battery. Caravan using car OK but not car using caravan.

 

[Keithmac]

With out 2013 Kuga (oem dedicated towing electrics) and 2008 Sterling you have to have the engine running and then turn on control panel in caravan for Fridge to work while towing. I believe as soon as you hook the towing electrics up it disconnects the caravan battery.

Heard plenty of people having bother with the new SMART controlled alternators and charging with the caravan fridge turning off when towing, some say towing with full headlights on negates this problem?.

What tow car hav you got?.

Only problem I've had was when refueling, turned the engine off which then turned the fridge off!. Was mulling over ways to prevent that but it's only an issue with out 400mile tow to Cornwall once a year!.

 

[Keithmac]

Other thing is you don't even need the caravan batter connected for towing, plus if you stay on sites with EHU you don't need a battery at all (apart from the mover).

 

[ericmark]

As said current towing vehicle does not have S socket connected, getting ready for next one, two vehicle supplies to caravan using cable colours red is only live with ignition on (or alternator charging) and green live all the time it is plugged in. Further tests show if I power red, then green also becomes live. But if I power green, read stays dead.

I found 5th fuse down connected green to red, left side live with green only and right side live with red only. However the voltages are interesting, I connected a voltmeter to green and powered red, the voltage shown is main caravan batteries voltage, not the 7 Ah batteries voltage used to emulate the car. So ignition live makes caravan battery connect to non ignition supply, it does not directly connect to ignition supply.

This kind of makes sense, it follows the BS7671:2008 regulations which says fridge and battery charging should not come from same supply.

If as with some cars the ignition switch as an auxiliary on it which powers down when starting then all the relay in car does is remove the load of fridge from ignition switch contacts. However if an auxiliary is not available then there were two methods, one connected to alternator warning light, so relay closes when alternator starts to charge, but this was dependent on alternator type, second method was a voltage dependent relay, this would only activate once volts over pre-set limit, so removed need to connect to alternator. However today both methods are useless, as battery volts and alternator charging is no longer maintained all the time engine is running.

This leaves a problem, if like found with my caravan the caravan battery is connected to car battery, it will equalise with car battery, i.e. be maintained at 80% charge unless engine on over run, which means if when connected caravan battery is fully charged, the car will discharge it rather than maintain it.

So the voltage dependent relay is no longer any good, and the charging paraphernalia has moved location from car to caravan, a DC to DC inverter will charge the caravan battery better than any split charging relay or blocking diode, but if a ignition activated relay is used in the car then part of start current can be drawn from caravan battery if not using a DC to DC inverter.

Now we reach the nitty gritty, unless you know how the caravan was wired, it is very hard to alter to match modern cars. And this is my problem, once I know how it did work, I can modify, but need to know how originally wired. To date it seems if I remove fuse 5 then it will just stop battery charging, and leave fridge and internal lights as they were. Still not a clue what fuses 2, 3, and 4 do, well 3 not connected so what 2 and 4 does.

 

[SimonH2]

I would be looking at the unit itself for a model number - then look for a manual online.
Things have changed since the simple (and reliable) methods I originally learned - one of them being that caravan loads cannot be run from the tow car with the engine running for EMC reasons. So you can charge the caravan battery, but the internal devices have to be disconnected from it.

 

[ban-all-sheds]

Personally I think it should be legal for anybody who encounters a caravan being towed between the hours of 06:00 and 24:00 on anything other than a 2-lane or up dual carriageway to set fire to it.

Just sayin'

 

[SimonH2]

How about it being legal to punch anyone advocating such destruction of property in the face. Just sayin

I'll just add that often it isn't the caravan holding things up - but that's all you can see from behind.
I recall one occasion with dad's van behind the landy, old turbo disease that wasn't exactly overpowered when solo. I was stuck behind a car that drove slowly - but speeded up when I tried to pass him. For the length of a dual carriageway section he exactly matched my speed to stay bumper to bumper level with me until I had to back off as the road returned to single lanes. For the benefit of other drivers I didn't try again - and guess what, he didn't speed up on the following dual sections, just held me up the ****
But guess who the people behind we're probably blaming for the slow progress

 

[ban-all-sheds]

Amazing, isn't it - all those people out there with an irrational dislike of caravans.

Makes you wonder why so many people could dislike them for no reason at all.

 

[ericmark]

Amazing, isn't it - all those people out there with an irrational dislike of caravans.

Makes you wonder why so many people could dislike them for no reason at all.

Old Top Gear and the guy who thumps people.

 

[ban-all-sheds]

One of the people he has thumped is Piers Morgan, so he's not all bad.