Jayco 2001 Westport wiring from trailer plug

Submitted: Saturday, May 12, 2012 at 20:21
ThreadID: 95522 Views:8648 Replies:5 FollowUps:10
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Hi all - hope someone has some info for me.

Before the explanation that follows the question is this:
In the wiring coming from the trailer plug there is a heavier black wire that connects under the van to 2 of the same gauge wires that both disappear into the van but only one appears in the wiring loom above this point that goes via a diode to apply positive voltage from the tow vehicle to the house battery/CS2000 converter system that is still factory standard it would appear. I am hoping someone might be able to tell me where the 2nd cable might disappear to within the van. It comes from pin 2 on the trailer plug (reverse light) but there are no reversing lights on the van.

More info if you want to know why:
My project is starting to come together and now I am playing with the 12V system on a Jayco 2001 Westport - and before we start "yes I am qualified to do what I am doing".

I am not looking to change much but want to improve the house battery charging system. I am seeing why Collyn Rivers and other forum articles refer to inadequate wiring in vans. I would like to know where the mystery cabls goes before I start changing things.
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Reply By: Member - Toyocrusa (NSW) - Saturday, May 12, 2012 at 20:44

Saturday, May 12, 2012 at 20:44
Hi Ken. It could be the power supply wire for 12v circuit on the fridge. Does seem strange that both are from the same supply though. Cheers,Bob
AnswerID: 485659

Follow Up By: KenInPerth - Saturday, May 12, 2012 at 22:36

Saturday, May 12, 2012 at 22:36
Thanks Bob - you have given me something to track down tomorrow.

I wondered if that would possibly be the case and that would make sense now that you have made me think harder about it. I am a novice at this but of course the only time you would run the fridge on 12V would be while travelling and I have probably read that when I think about it - imost fridges would not run off the house battery for very long would they unless you had serious house battery capacity.

The way it is wired if this is the case would also mean it cannot be run from the house battery as the diode blocks that from happening.

So given it comes from the reversing pin on the trailer plug this would also mean that the tow vehicle would have to be modified from "the norm" such that this pin supplies the charging voltage from the tow vehicle - but maybe this is "normal" if towing a caravan with a 7 pin plug. I am new and naive in this department.

It makes me think though "how many people set their fridge to 12V while they are travelling thinking the fridge is being run on 12V and it is not happening because their tow vehicle has not been modified??


FollowupID: 760918

Reply By: 93maverick - Saturday, May 12, 2012 at 20:48

Saturday, May 12, 2012 at 20:48
If you have a breakaway system, it might go there to charge the internal battery in this system.
AnswerID: 485660

Follow Up By: KenInPerth - Saturday, May 12, 2012 at 21:38

Saturday, May 12, 2012 at 21:38
Thanks but I don't think that is it.

It does have electric brakes but no breakaway system.

There is no voltage on this lead on the trailer plug side of the diode either.

The way it is wired the diode would block the house battery from providing any power back on this cable - by logical reasoning it can only be a supply from the tow vehicle and the diode prevents the house battery discharging back into the tow vehicles system.

FollowupID: 760916

Reply By: KenInPerth - Saturday, May 12, 2012 at 22:57

Saturday, May 12, 2012 at 22:57
Just a follow up on tihs for those that may be interested.

The wiring diagram supplied with the Jayco for the Centurion converter (which I have in the original owners manual supplied with the van and that I have also seen on other posts) is not the way the actual wiring is - and there are no signs that the wiring has been modified to original factory condition.


AnswerID: 485667

Follow Up By: jacent - Sunday, May 13, 2012 at 10:02

Sunday, May 13, 2012 at 10:02
Mate, jayco spare parts shop in dandenong, Victoria were very helpful with questions ihad on my 88 jayco, they keep all records on the computer of every jayco they ever built aus wide and can look it up if you supply your chassis/vin no. I was asking about fitting an air con and they were able to tell me that mine had been pre wired ready to instal one back in the day just by supplying them the chassis no . Maybe they may have details on how your van was wired from factory if it was customised possibly? Hope it may help?
FollowupID: 760934

Follow Up By: KenInPerth - Sunday, May 13, 2012 at 10:18

Sunday, May 13, 2012 at 10:18
Thamks Jacent - I wil keep these guys in mind. Good information.

I think Bob and some other articles I have seen (eg. one from Derek at Sidewinder) will be the way it is - the fridge wired completey seperatley.

In fact when I read the Jayco manual more cosely re the fridge and operation it says you need to get it wired to the battery of the car for 12V opeation but does not give any detail in the handbook about how the trailer plug is wired. This would also tend to confirm it.

People that deal with caravan and trailer plug modifications for tow vehicles will be reading this post in "disbelief" as it is all probably quite "normal and standard" within the industry - even though it would mean that when you hook up a standard trailer after the modification to the tow vhicle the reversing lights would always be on (if it has reversing lights ....)

Anyway I will be changing to a 12 pin plug to "standardise" the plug wiring a bit better.


FollowupID: 760936

Reply By: KenInPerth - Sunday, May 13, 2012 at 15:53

Sunday, May 13, 2012 at 15:53
OK - just for the record in case it is of use to others.

Pin 2 of the trailer plug comes into the van and is wired direct to both the fridge for 12V operation and the anode of a diode on a heatsink.

The cathode of the diode goes to the battery and the 12V output of the Centurion CS2000 - one would assume the only real purpose would be to provide 12V charging to the van battery when travelling, although under these conditions it also powers the other 12V circuits in the van via the CS2000 outputs - as per the drawing I have seen from Collyn Rivers I assume.

AnswerID: 485707

Follow Up By: Member - Toyocrusa (NSW) - Sunday, May 13, 2012 at 19:45

Sunday, May 13, 2012 at 19:45
Hi Ken. Looks like you are getting on top of things. As you have said in another reply, wire the fridge and charge through a 12 pin plug.(separately) Also wire the fridge supply (in the car) through an ignition cutout system so that it only supplies power when the engine is running. As you have stated, the fridge requires a lot of current and will flatten any battery within an hour or so. I ran mine through a 50amp relay. A friend ran his through a small solenoid which should be even better for voltage drop. I know members "john and val" have a good electrical blog on here somewhere but I just tried to seach for it without success. Maybe you could PM them. Cheers,Bob.

FollowupID: 760977

Follow Up By: Member - Toyocrusa (NSW) - Sunday, May 13, 2012 at 19:52

Sunday, May 13, 2012 at 19:52
I think this is it.
Electricity for Camping

FollowupID: 760983

Follow Up By: KenInPerth - Sunday, May 13, 2012 at 22:57

Sunday, May 13, 2012 at 22:57
Thanks so much for that reply - more good information.

Yes I intend to have a cut out method such that it will only supply power from the tow vehicle when it is running for the exact reasons you mention.

Once again - thanks to you and the others that replied.

FollowupID: 761001

Reply By: Nomadic Navara - Tuesday, May 15, 2012 at 00:44

Tuesday, May 15, 2012 at 00:44
Keith, you are on the right track with the wiring of your van. Here are a few other snippets for you.

In the standards for trailer plug wiring provision is made for reversing lights (often termed reverse signal.) Here are the standard configurations. If you have a Toyota and the Toyota agent wired the trailer socket you will probably find it was wired to the standards. People plug their vans into the tug, turn the fridge to 12 V and when they apply their brakes the fuse blows. They also loose their electric brakes as there is no brake light signal going to the brake controller after the fuse blows.

In the normal scheme of things, tow bar installers ignore ignore the signal pin as they consider that no trailers have reverse lights (some do including mine.) To keep the installation price down they also don't include the hot wire to the tugs battery unless you ask. At least that's how things work over this neck of the woods.

When over in WA a few years back i noticed you people use the small round 7 pin connectors. If you are using them I suggest you change them. If the hot wire is large enough to run the fridge efficiently then it will burn out pin 2 by overloading it. You will also possibly find the wiring in the van is a little light on to carry the battery charging and run the fridge.

I suggest you use the 12 pin connectors, they have 7 pins the size of the little round ones and 5 larger pins suitable to run the fridge. Add an extra wire to the fridge (or the battery if that is easier.) Use 8 gauge wire minimum. Wire the fridge through pin 9 and the battery through pin 8. For the tug, run separate wires back to the battery. I have a couple of relays in my system. The one in the fridge line is switched via the run position on the ignition switch. The one for the battery runs in the accessories position. This prevents the fridge from flattening the cranking battery when you stop for a break. When you rewire the van this way you can also now get rid of the diode and get more voltage to your house battery for a bit quicker charging.

If you don't have enough coper in your system you will get excessive voltage drops. You may see current ratings on the reels of wire, ignore them, they are just currents that will not significantly heat up your wire. Even if you are using wire with twice the current rating then you will be loosing too much power over the distance you are running your wires. Read about it here.

The Centurion power supply in your van (like the Setec also used by Jayco) is an excellent power supply for running your 12 V system in the van. However it is not a very good battery charger. I would suggest that if you want quick battery recharging during one night stands in caravan parks you also should have a multi stage charger wired to your battery for 240 V charging.

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AnswerID: 485848

Follow Up By: KenInPerth - Tuesday, May 15, 2012 at 10:36

Tuesday, May 15, 2012 at 10:36
Peter - thanks for taking the time to post this information. Fortunately, and being an ignorant novice at this point, I have since found my Patrol had been modified to tow a van before I got it - presumably by the guys putting in the brake controller also ran in the battery wiring - to a 7 pn plug no less.

One query though - when you say "apply the brakes and the fuse blows" do you mean "put it in reverse" ?? It is the reversing pin hooked up to the firdge via the caravan plug??

I am however on the path of everything you mention.

I am changing to 12pin plugs and sockets as part of this project to help standardise the wiring and get higher current rating on the pins for battery and earth, exactly for the reasons you mention. As you say it seems rare in WA to find better than 7 pin small on most things.

I am well aware of the problems with cable ratings and using enough copper - it frustrates me no end the way cable is advertised in media and on packaging - but if you challenge them on it they either have no idea or argue the point - "Ohms law - what's that" ?? Even a few of what I would consider more reputable and ethical suppliers fall foul of this bad rating to entice people to buy inadequately rated cable for purpose. Sidetracking, I saw an "800Amp" all in one jump start kit the other day which could not have had more than a 12V 7AH SLA battery in it and the purchaser wondered why it was not starting his car - I measured about 4V at the battery when trying to start the car with it.

I am also going to isolate the car system from the van as you mention and will have provision for a good multi stage charging system for the batteries. I have seen a lot of "bad reviews" of the Centrurion, but if I recall correcty it is mainly for what you say - it is not a battery charger and hence the need to put something additional in. I think Collyn Rivers states it is not regulated either and pretty basic, but for what it is designed to run (mine is max 20A running low power 12V lights and a water pump) it seems fine to me for purpose and is designed to allow the house battery to supply the loads when not on 240V.

Thanks again for yur input


FollowupID: 761095

Follow Up By: Nomadic Navara - Tuesday, May 15, 2012 at 14:09

Tuesday, May 15, 2012 at 14:09
Quote "One query though - when you say "apply the brakes and the fuse blows" do you mean "put it in reverse" ?? It is the reversing pin hooked up to the firdge via the caravan plug??"

Thanks for picking that up. I sometimes get wires crossed in these early morning replies. I should have said reverse light blows when they reverse the rig. First time I heard of Toyota dealers wiring the sockets to the Oz standards was when CW did a tow test on the then new Cruiser 100s. The first they knew of the blown fuse was when they could not lower the windows. The power windows are on the same fuse as the reverse lights.

I came upon the 7 pin small round standard connectors when my previous tug (Disco D2) was in Barbagalos for some time. I had occasion to shift my van. We went right around their yard and all their vehicles had that socket. Then someone remembered they had a trade from NSW stashed away. It had the flat 7 pin socket which saved the day..

I'm not sure about the regulation of the Centurion but I know the Setec is fairly good. The big problem with both is the lack of a sufficiently high enough voltage to charge the battery.

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FollowupID: 761113

Follow Up By: KenInPerth - Tuesday, May 15, 2012 at 15:01

Tuesday, May 15, 2012 at 15:01
Just for info, on "no load" the Centruion I have is putting out about 13.3 Volt which as all the vaious articles say will not do a lot for fully charging the battery - but at least I guess it is better than nothing in those cases where they have nothing else added to the system.

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