Interior 12 volt electrics

[PaulA3]

I have just replaced my 1990 Fleetwood Garland with a 1998 ABI pioneer Rallyman and I am about to set off on our first outing. The dealer ran through everything with me when I picked up the van, or so I thought I have just connected the 12s plug and found that the van works in a totally different way to the Garland. When the engine is running the interior 12volts don't work on switching engine off they work I read the manual thinking there was a fault only to discover this is how it should work.

My question is why I don't see the logic of going to the expense of fitting a relay to disconnect the internal 12volt electrics does anyone know why this is done ?

 

[ProfJohnL]

Hello Paul,

There was a change to the wiring arrangements for the 12S socket a few years ago and your two caravans probably straddle this change.

I strongly suggest you have an auto electrician check out your car for compatibility to the new standard. He/she will also be better able to explain the effect the new wiring has.

 

[PaulA3]

Hello Paul,

There was a change to the wiring arrangements for the 12S socket a few years ago and your two caravans probably straddle this change.

I strongly suggest you have an auto electrician check out your car for compatibility to the new standard. He/she will also be better able to explain the effect the new wiring has.

Thanks John I asked the question because I am an electrician admittedly not a auto electrian. I am puzled as to why this change was introduced as I can not see a logical expanation.

Now I'm back from our fist trip there are a few things I want to change about the caravan this being one but dont want to change it untill I know why they did it.

 

[rayc]

Paul, I believe it was European standardisation regulations which said that you must not be able to have the interior lights on when van is being towed, so this was the solution. When the power is switched off it is fed to the van battery for charging i.e the permanent feed and the battery charging is a combined feed on post 98 vans whereas in pre 98 it was two seperate circuits.

The relay that switches the power circuit on / off is activated by a relay in the van that is operated by the fridge supply.

 

[PaulA3]

Thanks Ray But why have they brought this rule out, is for safty reasons if so what is at risk, I can understand gas being turned off but not the interior lights ?.

 

[rayc]

Paul, as I said I think it was to comply with a European Harmonisation regulation that said you must not be able to switch the van internal lights on when the van is being towed. It also freed up the battery charger feed that is on pin 2 on pre 98 vans. Pin 2 was then designated for 'Coding for coupled trailer', that is to tell the driver that the caravan is attached. It has never been used for that by UK caravan manufactures although I would expect a caravanner to notice if the van was attached or not. I can see its application in a box van with a trailer where the driver may not be able to see it when travelling in a straight line!!

I hope this helps you in your quest for understanding the electrical circuits, though possibly not the thought processses of the regulors who drafted it, and the benefits that being a member of the European Community has brought you.

 

[PaulA3]

Thanks again Ray I'm going to have to get the test meter and tool box out and find out what they have done.

I have a battery in the boot charging from the engine via a split relay I connect the van to the car when on site to trickle charge from this battery to the caravan battery and if as you say they have done away with the seperate caravan charging pin it will not work.

I just cant see the logic but I'm sure they have a reason perhaps to make us fitter carrying batterys.

Other things I am not to pleased with include small water pipes and bib taps so it takes longer to fill the sink so the pump is running longer draining the battery this is probably to save water but I can fill up with more water on site, charging a battery with out electric up is not so easy. I have two flouresent lights under the curtain pelment they dont work if not on Electric hookup yet the reading lights using high wattage bulbs do running off the battery surly the othe way round would make more sense, conserving the battery.

 

[rayc]

Paul, You could time share the load instead of trickle charging the van battery with the in boot battery. Connect an isolator switch to the van battery, connect the boot battery to pin 4(+) pin 3(-), this would in effect parallel up the boot battery and the car battery which should already be connected this way. When you switch the van battery off the 12v should run of the boot battery / car battery combination. As you say the 12v strip lights should run direct of the battery supply not require any mains, so either there has been a mod of some sort or they are not original equipment.

Good luck I'd better leave it at that before I say something to cause your van to blow up!

 

[PaulA3]

Thanks Ray I have been reading the vans hand book and as you say pin 4 is spare, apparently you can have an other problem with this system, if the car battery is fully charged ie over 13 volts it will keep the relay closed and not allow the interior 12 volts to work you either have to disconnect the 12s plug or turn the car head lights on for a few minuets to drop the car voltage. Who comes up with these ideas certainly not caravanners.

So I am going to disconnect the caravan relay, run pin 4 to the battery and save all that battery carrying.

 

[rayc]

Paul, I hope I havn't confused you, I didn't think I said pin 4 was spare, I thought I said pin 2 was. Pin 4 should be your permanent feed / battery charge from the car so it should already be connected to the car battery. If your caravan handbook says that pin 4 is unused it is wrong.

Be aware that the relay operating coil is fed from the fridge supply on pins 6 & 7.