12pin trailer plugs for Caravans - needed?

Submitted: Friday, Aug 14, 2015 at 09:56
ThreadID: 129985 Views:3199 Replies:2 FollowUps:12
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Bought a caravan privately, it has a 12pin plug fitted standard as do most. But it also has an anderson connector fitted for 12V feed from the car.

So do I need to run a 12v socket on the car? from what I can see from the wiring pinout diagrams, the extra 5 pins are for aux power for battery, fridge etc. Wont all these things run fom the onboard battery pack in the caravan which I can keep topped up through the Anderson connector as we drive?

Jayco Starcraft Outback factory setup if that makes any difference. Thanks
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Reply By: Frank P (NSW) - Friday, Aug 14, 2015 at 10:45

Friday, Aug 14, 2015 at 10:45
Boxer,

If your van has a 3 way fridge the Anderson might have been installed to help it run on 12V while towing. It might also have been installed to improve charging of the van battery while driving. In either case the 12 pin plugs and sockets cannot accommodate the cable size required to make a 3 way fridge work on 12V, or to optimally charge a van battery so far back from the alternator.

If the Anderson has been done correctly, it will have heavy cable. 6 or 8 B&S, preferably 6. Considering that the van has the Anderson, I would be inclined to set up the car to accommodate it. You need to have matching cable in the car back to an Anderson, and an isolator. The isolator can be a simple ignition-controlled one.







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Follow Up By: B0XER - Friday, Aug 14, 2015 at 10:51

Friday, Aug 14, 2015 at 10:51
Thanks Frank, that was my understanding too (yes the Anderson is heavy gauge) so why the 12pin plug as well?? Its a full factory setup not done aftermarket
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Follow Up By: Frank P (NSW) - Friday, Aug 14, 2015 at 11:15

Friday, Aug 14, 2015 at 11:15
Don't know, mate. Maybe the previous owner specified it at purchase.

Does the wiring diagram give any clues? Or can you trace wiring on the extra pins?
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Follow Up By: patrolman2 - Saturday, Aug 15, 2015 at 14:33

Saturday, Aug 15, 2015 at 14:33
It is a good idea to have a 12 pin plug even if you do not use the total capacity.Remember, the fridge and the on board battery should be run through Anderson plugs connected with 6 B&S wire and through a solenoid.Remember also the battery in the breakaway unit needs to be charged and one of the unused poles in the 12 pin plug can be used for this purpose and if you have a visual and audible monitor as required by law in NSW,this also can be wired through a vacant pin.Any safety system fitted to your suspension would use up another terminal……what else can we add?
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Reply By: Member - Phil G (SA) - Friday, Aug 14, 2015 at 16:56

Friday, Aug 14, 2015 at 16:56
I've just bought a caravan with a 12 pin plug.
8Ga wire can go into the large pins of the Narva 12 pin - I just tried it.
Pins 1-7 are standard and include the electric brakes.
pin 8 is used to supply the 3-way fridge power when driving and for Brakesafe charging
pin 9 is used if fitting the Brake safe remote
pin 10 is an 8Ga earth return
pin 11 blank
Pin 12 is for the Dometic AES sensing wire if fitted.

In addition there are 2 anderson plugs:
Grey Anderson plug is used purely to recharge the caravan battery.
Red anderson plug supplying power for the Alko Electronic Stability Control
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Follow Up By: Frank P (NSW) - Friday, Aug 14, 2015 at 17:58

Friday, Aug 14, 2015 at 17:58
Thanks Phil,

I didn't have much success with a 12 pin plug and socket. The currents drawn by the fridge and my dc-dc charger in the van stuffed the large contacts in the plug/socket that those circuits were using. Fridge 12 amps, charger 30 amps.

I hope your experience is better.

I converted to a 7 pin large round with big fat contacts to run the normal 7 pin stuff plus an Anderson with 6ga cabling to take power from front of the car to the electrical board in the van, which was right down the back, so a l o n g cable run. Voltage drop on the long cable run combined with the low output from the vehicle charging system was an issue at the time (2007 Prado, 13.2 volts), so I went with the 6ga cable.

My new BT50 settles at about 14.4 or so volts, much better. 8ga could well be adequate now, but I wired it with 6ga because I could, I guess. I didn't want to run the risk of having to re-do it.
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Follow Up By: Member - Phil G (SA) - Friday, Aug 14, 2015 at 23:17

Friday, Aug 14, 2015 at 23:17
Gday Frank, your experience is probably why the caravan company uses 2 anderson plugs as well as the 12 pin socket!
I also like the large 7 pin round - it was very common here in SA.

But realistically the currents of the brake/clearance/tail/blinker lights is less as they are all LED.

And Marine (tinned) 6B&S is what I have now going to the grey anderson plug. Got no idea what happens to it on the caravan side, but if it doesn't have a DC-DC charger, I'll probably put one in.
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Follow Up By: mack c - Saturday, Aug 15, 2015 at 01:42

Saturday, Aug 15, 2015 at 01:42
Hi.

Those large SA round have a big problem.

I had one yrs ago on caravan. up in Qld one yr. the centre wire (earth) came adrift.
and spent half of it's time shorting out the brake wire.
By the time I'd realised it the brakes were cooked.
Small 17ft caravan behind patrol didn't feel it.
Travelling with friends, very hilly country and occupied.
Got to Cania. Paint cooked on drums and had to file burnt material of brake shoes to carry on.
And it had just been all rewired by Pro Electrical dealers in NSW to suit my SA reg's vehicle. Hence the plug change.

It happened once b4 too.
The flat 7pin are the better ones I think after 400 odd yrs towing in different States in this country.
with one or two Anderson type for charging and fridges etc.
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Follow Up By: Member - Phil G (SA) - Saturday, Aug 15, 2015 at 04:42

Saturday, Aug 15, 2015 at 04:42
mack c,
If you lost the earth, then I'd guess you'd know because none of the lights would work. At least the good brake controllers these days would tell you nothing is happening at the brakes.
Maybe you reinforce why I do my own wiring - that sort of thing is poor workmanship, rather than the plug.
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Follow Up By: Phil 23 - Saturday, Aug 15, 2015 at 08:03

Saturday, Aug 15, 2015 at 08:03
What's a Break Safe remote Phil?

I've found the 12 Pin expalnations to be a bit conftadictory from site to site.

Ie, 8, 9 & 12 can be power.
Is one of those intended to be relay switched with ignition.

Have a look here:-
https://www.google.com.au/search?q=12+pin+trailer+plug+wiring&biw=1366&bih=598&source=lnms&tbm=isch&sa=X&sqi=2&ved=0CAYQ_AUoAWoVChMI9NrQ9sepxwIVZCSmCh3MrQGz

and you'll see what I mean about a lot of diagrams contradicting others.

Cheers.
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Follow Up By: mack c - Saturday, Aug 15, 2015 at 10:33

Saturday, Aug 15, 2015 at 10:33
Yes Phil.

The point being. mainly.
That plug being round, wires in a circle.

Nobody is perfect all the time.
It CAN happen with the round ones.

Flat plugs. No way they isolated with dividers
and can't fall on top of each other.

I normally do my own too.
But. New Interstate van. Rego over the pit.
In a hurry.
big name 12v reputable dealer/Workshop.
(one of the biggest in fact) not giving name.

You don't expect that.
Somebody had a friday arvo hey.
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Follow Up By: Member - Phil G (SA) - Saturday, Aug 15, 2015 at 11:18

Saturday, Aug 15, 2015 at 11:18
Gday Phil,

Breaksafe is Redarc's version of the breakaway system compulsory on vans over 2T these days. It has it's own battery that is recharged off pin 8. The remote is the optional monitor that sits on the car's dash and when the LED is green, indicates the Breaksafe's battery has sufficient charge, when red, indicates insufficient charge. So pin 9 is used to supply signal from the caravan to the remote.Here's the manual.

You are right - there is a lot of variation depending on what is fitted to the caravan. But I expect that pin 10 is always earth, and what you do with the other 4 large pins is up to the user.

I did the wiring for a mate's Ultimate Ultra camper, and on the 12 pin plug, they bridge two pins (8 &12) for pos and two pins (10 and 11) for earth. So the extra pins are used to double up on capacity as they have to power the 3-way fridge as well as charge the camper batteries.
Pin 9 is used for the IGN signal wire to let the Dometic AES unit know when the engine is running.

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Follow Up By: Frank P (NSW) - Saturday, Aug 15, 2015 at 22:55

Saturday, Aug 15, 2015 at 22:55
Phil G (SA) wrote in Followup 857071

"And Marine (tinned) 6B&S is what I have now going to the grey anderson plug. Got no idea what happens to it on the caravan side, but if it doesn't have a DC-DC charger, I'll probably put one in."

Based on my mate's 200 Series alternator output, I think a dc-dc charger would be a good idea, Phil. He was getting 13.2 volts - not enough to fully charge a typical AGM house battery, especially at the end of a long cable run.

Flame suit and crash helmet on ...
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Follow Up By: Member - Phil G (SA) - Sunday, Aug 16, 2015 at 06:14

Sunday, Aug 16, 2015 at 06:14
" flame suit and crash helmet on".....haha you can't suck me in that easily....or maybe you can :-)

But for a caravan battery, I don't think there is any doubt I'll want a DC-DC charger. The Tvan has had a CTek D250S for a few years, and I used a second one in the 200 until it cooked the auxillary battery under the bonnet on a 47 degree day and I had the unit mounted in the cool air cond cab and was too lazy to extend the temp probe under the bonnet.

But 13.2V?? Must have a different 200series to mine or he's measuring voltage only at idle (it drops off a bit at idle, so using a multimeter under the bonnet at idle is useless) or he is using a scangauge to measure voltage which is 0.3V lower than at the terminals.

Driving along, and its cool I see 14.1 down to 13.7. I've rarely see mine below 13.5V. When its been 45 degrees on a "normal" SA summers day, I've seen 13.35, which is appropriate under the bonnet. Gets a bit warmer under the bonnet than previous vehicles I've had because there's less ventilation with all those guards underneath.
Cheers
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