My Bailey Unicorn 2 Cartagena is having issues charging the leisure battery from the towing vehicle and running the fridge. It charges fine and fridge works when hooked up to mains or gas and the solar panel is charging the battery fine. When I hooked the car up and turn on the engine, the fridge fuse would melt, not straight away but after about 5 mins. All other fuses are fine. Now the fridge will not run at all while hooked up to the car so we have to keep it off when travelling. I have heard it may be a relay problem but I can’t find any details on a relay from the wiring diagram for this model of caravan. Can anyone help?
Bailey Unicorn 2 Cartagena not charging from towing vehicle
- Thread starter Hermitcrabs
- Start date
If a fuse melts, it indicates that to much current is passing. As the Fridges 12V element will only operate when its connected to a tow vehicle and the engine is running, it points to a possible failure of the element.
What rating of fuse is fitted? If you have an under-surface fridge you are likely to be pulling around 120W so you would need at least a 15A fuse to provide some headroom: if you have a tall fridge (unlikely I suppose in a U2) they pull more like 170W so a 20A fuse would be appropriate.
If, like my present U4 Seville, the fuses fit into holders in the front of the power box at the side of the mains MCBs etc the holder is probably contacts soldered onto a piece of printed circuit board. If the fuse melted there would probably have been enough heat to melt the solder and destroy the connection. A good bright (LED) torch and whatever you need or not to have a closeup look at the contacts is the best option. DO NOT start taking the power box apart unless you <really> know what you are doing.
If, like my present U4 Seville, the fuses fit into holders in the front of the power box at the side of the mains MCBs etc the holder is probably contacts soldered onto a piece of printed circuit board. If the fuse melted there would probably have been enough heat to melt the solder and destroy the connection. A good bright (LED) torch and whatever you need or not to have a closeup look at the contacts is the best option. DO NOT start taking the power box apart unless you <really> know what you are doing.
The fridge has a very small heater that runs on 12 volts. Looks as though that has gone and the broken element is shorting out. Need a technician probably.
If the element was shorting the fuse would blow instantly, not by overheating after perhaps 5 minutes as the OP states.
Ok. So would that have anything to do with the battery not charging? It just seem to all happen at the same time which I found a bit odd.
It really is not possible for me to remotely answer that. You have a fault of some sort, It is as Woodentop suggests a strange one as a full short would cause the fuse to instantly blow. Even though we are talking about 12V systems which wont give you a shock, the battery has more than enough power to start a fire if any of the wiring or connections are suspect, so it really needs to be investigated by someone who knows what they are doing.
The power fuse's on my Santa Fe, there are two. One for the caravan running lights and the other for Fridge/battery charging, are both 15 amp.
On my 2013 coachman, the fridge and battery charging fuse's are 6 amp in the main consumer unit. Check your fuse's on the car supply side, one of those might have gone as well, causing the battery not to charge from the cars electrics.
On my 2013 coachman, the fridge and battery charging fuse's are 6 amp in the main consumer unit. Check your fuse's on the car supply side, one of those might have gone as well, causing the battery not to charge from the cars electrics.
When you talk of 6A fuses on the fridge and charging do you mean fuses as in 12V or do you mean MCBs as in mains? I suspect the latter.
If the fridge is the under-counter type it will probably pull about 10A (120W) so 15A <should> manage it provided the battery is on the healthy side. Nonetheless I would have put in a 20A - after all it is there to protect the cable more than the fridge.
If the OP has a voltmeter of some sort then checking the car fuse(s) is more easily done by measuring at the 13-pin socket. Negative for all except the fridge is pin 13, pin 9 is the permanent 12V and pin 10 (with pin 11 as its negative) should only be 12V when the engine is running. The pin layout and numbers are are on the inside of the hinged cover.
If we are talking 12S connector, 13=3, 9=4, 10=6 and 11=7.
Thank you all for your advice. I have checked the car fuses and they are absolutely fine. I also checked at the hook up point and for continuity which again was working fine. The fridge is a tall model not an under counter. I have attached a picture below of the main fuse panel. the far right is the fridge one which keeps melting whenever I try to run off the tow vehicle. the panel states 15A but I put in a 20A however it still melts when towing.
Attachments
Not towing right now. We were towing in France and Spain but now back in the UK and parked up till we can travel again.
A tall upright fridge such as a Dometic RM9330 as we have in our U4 Seville will pull about 170W or near enough 15A so a 15A fuse is pushing your luck a bit. Look in the caravan handbook for the exact power drawn.
One question: does the fuse still melt if the van is connected to the car, the car engine is running but the fridge is turn off? If it does then it could be a wiring fault: if it doesn't then it is the fridge and as others have suggested it could be a short or a partial short on the fridge 12V element. If your meter can read resistance, 170W at a nominal 12V should equate to a resistance of about 14 ohms. If it is less than that then the element may have a partial short on it (i.e. the element has deformed and it has touch the surrounding chimney part way along the element.) On the other hand if the resistance is much less than 14 ohms (usually these days written as 14R) then you could have a shorted element and the resistance you are measuring is that of the cable which could be getting very hot and may cause a fire.
One old trick is to remove the fuse, find the red and black (usually) 12V wires going to the fridge (under the adjacent bunk or at the back under the cooker depending on relative positions) and stick some pins through the insulation into the wire. Then switch the fridge on at 12V and measure the resistance across the element. By doing this you are essentially looking only at the element and not the power cables.
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