Electrical 7 pin wiring

[Drover]

At least I don't let myself get into the position of flat car battery as Big Mal unless I leave fridge plugged in as no 12v supply to van, fridge goes on gas anyway and I lift weight off ball so unplug .............
I really need to fit a relay on the fridge, my fridge run anderson is 6B&S, huge stuff with anderson at fridge as well which I use as a step down for the cable to plug into the fridge circuit, this also makes it a handy 12v extension lead to rear of van if needed (22ft long so helps)...........

When a breaksafe is added it makes things even more confusing trying to track things down............even with the diagram....

 

[Boots in Action]

Hi @Boots in Action,
all correct except:

Pin 8 is not used in the standard Jayco wiring. Refer to the pdf relating to 12-pin wiring that I posted earlier. This is exactly how my van came wired from the factory (and still is).

Pin 2 goes only to the Setec Aux in. From there, within the Setec it will charge the battery if fitted and supply 12V to power the van if a battery is not fitted (or if the battery isolation switch is inadvertently left off).
The original thinking at Jayco, when it was not common for a battery to be fitted to the van, was to enable the car to supply 12V to the van when off grid (stopping overnight on the way to a caravan park). So, pin 2 needed to be hot even when the engine was not running. Naturally, this was really only intended to power a light or two and light the stove. But that was way before 12V television, charging multiple phones and tablets, fans, fridge fans, etc became common.

Still a trick for new players with a van battery is to pull up for a quick overnight, leave the tug connected, leave the battery switch off, and bask in the warm glow of having a van full of 12V, only to discover the next morning that all that lovely 12V was coming courtesy of the car battery which now has insufficient charge left in it to start the car. I suppose, to be on the safe side, if a van battery is fitted, it would be prudent to disconnect the 12V plug to ensure the car battery is not discharging into the van. I don't bother, since 1: I know what I am doing, 2: our 12V usage at night is minimal, and 3: I will eventually live to regret making statement 1!!!! Although with lockdowns and the inability to even consider when we might go camping again, I would probably love to be in a position where my only worry was a flat car battery and no phone signal to ring the RACV.

Continuing:
There are only two wires on the heavy duty pins of the 12 pin plug, pin 9 for the fridge 12V, and pin 10 for the fridge ground.

take care
Mike

Thanks Mike @mikerezny for the clear explanation of how connections from tug to trailer/van have evolved over the years owing to necessity and demand for extra features.
In the first place, a 7 pin plug was really only suitable for box trailers and the like. Having only 7 circuits, there was no line for 12 volt power to be carried from tug to van, only for indicators, stop lights, brake and width lights etc. Then someone decided to use pin 2 (hijacking the reversing light circuit). This saved running an extra separate line from tug battery to van. The only problem there that I could see was that it would have been necessary to have (while still hitched up) the engine running, the ignition switched on, or switch on Accessories. All these meant that the keys had to stay in the ignition to keep pin 2 "hot" for lights in van to operate if you did not have a van battery. Take keys out, or turn off switch, and no power to reversing light circuit!!! Otherwise, run a separate power line from tug battery to connections on van for lights etc Now 8 circuits involved!! . At that stage there was no thought or provision for a separate battery in van or to charge it from tug.

Then came the need to run electrical equipment in van whilst driving - the fridge among them. But all circuits are now utilised, so enter the time of separate circuit from tug to van fridge using high current cable and Anderson plugs. My van started with a 7 pin plug and extra wiring for fridge with Anderson plugs and heavier wiring. And then, came the requirement to put some charge into van battery from tug electrical system. Using the old pin 2 with only a light wire (AWG 12 as suggested by Jayco) over at least 7 metres with that sort of resistance and then through a power diode (with its inherent voltage drop) meant that the charging of van battery was extremely limited, no matter how long or far you travelled. Then to make matters worse, tug manufacturers decided to do away with fixed voltage regulators on alternator outputs in the name of greater vehicle efficiency, and introduce "smart" alternators with temperature or electronic controls with lower voltages. That made it even harder to charge van battery from tug!! Enter the necessity and need for DC-DC chargers. No extra circuits but more wiring to have installed.

While these changes were going on, the introduction of a 12 pin connector came into its own. It had the usually 7 pin arrangement for vans and tugs such as indicators brakes, stop lights etc) PLUS an extra 5 heavy duty connectors for fridge power and battery charging too if pin 2 was no longer used. Now we have at least 9 circuits (in its simplest form) between tug and van which meant that extra wiring was needed in tug harness, disregarding any control equipment in the lines!!! And even then, not all circuits/pins are utilized!!!

Whilst tug and van manufactures may have their own recommendations for hookups, many of us have used our own electrical skills to improve the system by modifying the wiring connections. Whilst I believe that I have good electrical knowledge on 12 volt wiring, I am finding out that it is not so hot on van wiring without a circuit diagram!!
However, I seem to have "stumbled into accuracy" with my setup as below.

Fridge is still connected between tug and van by separate dedicated lines with Anderson plugs and via VSR.
Pin 2 on tug is still operational and allows reversing lights to operate when connected to my box trailer with 7 pin plug connecting to the lower half of my 12 pin socket on tug. On van, I have no connection to pin 2 and hence no power from tug to van battery in that circuit to Setec , nor through the power diode to prevent battery leakage to tug battery and protect wiring. And power to battery from tug is now direct to battery +ve pin 8, just like connecting a 12 volt solar panel across battery terminals. This should provide a higher voltage and more direct current to charge battery. The negative return is via pin 10 direct from battery.
Now two things are important here. Van battery charging is controlled by tug alternator (fixed voltage type) and as no power diode in this circuit, feed back leakage from van battery to tug battery is eliminated by the voltage sensing regulator which breaks this circuit when tug battery voltage drops to 12.6 volts or lower. This would definitely occur when tug starter circuit operated. The VSR re-connects the line to charge van battery when tug voltage reaches 13.2 volts or higher. All my heavy current wiring coming from battery goes through a 80A fuze (auto reset), then through the VSR before going to their separate fused circuits and different pins. All wiring is AWG 8, to minimise voltage losses and maximise current carrying capacity.

So summing up, I still have my reversing lights working, believe I have improved van battery charging, but fear that I will never be able to run without battery in van, or run fridge from 12 volt battery in van, something I am not contemplating at all. No problems since making these mods a couple of years ago.

Over to you Mike for your critique.
Cheers

 

[mikerezny]

Hi @Boots in Action,
indeed pin 2, normally reversing lights, has been hijacked for Jayco. It is intended that the existing wire on pin2 is removed and insulated.
A new wire is added to pin 2 that is connected to a permanent source of 12V in the car. This overcomes your discussion of having to leave the keys in the car, and ignition switched to accessories etc.
In my Falcon, the brake switch is basically a normal old 12V permanent in and the other side wired directly to the brake lights. There is also added switch contacts to tell the cruise control to sod off if the brake pedal is pressed.
So, the hot side of the switch has been wired back to pin 2 of the trailer socket and the brake side goes to the brake controller.

In a perfect world, Jayco would leave the 7 normal pins to perform the standard function, running all the external trailer lights, including reversing lights and electric brakes, with the earth return being used only for those items.
Pins 9 and 10 would run the fridge, and two of the three remaining heavy duty pins would be used for the 12V to the Setec AUX input to run the van lights, stove ignition, etc if no battery is fitted in the van and to charge the van battery, if fitted.
But the current wiring has been around a long time now and grew from the 7-pin days.

I like your idea of using a VSR and bypassing the Setec Aux input and its protection diode. This indeed gets a higher voltage to the van battery. A VSR is a necessity, as you pointed out to prevent the van battery being used to start the tug.

In the early day, I considered doing the same, but in the end, I wasn't all that fussed about relying on the tug to recover the battery since our 12V power usage is minimal. But in the end, I am a tight arse and I didn't want to spend the money on a VSR. I would probably have rather spent the money on a larger solar panel.

take care
Mike

 

[Drover]

My goodness, War and Peace post there...

 

[Boots in Action]

My goodness, War and Peace post there...

Really just an exchange of ideas between two "Tech Heads" and for others who may be interested. I hope I did not lose you with the technical explanations.

 

[mikerezny]

My goodness, War and Peace post there...

Hi @Drover,
that is what happens when you live in Melbourne and lock people up. This forum is one of the only outlets Dan Andrews hasn't found a way of banning.

As soon as we are allowed to mingle and go camping again, I won't have time to write any massive posts. Hopefully, I will be able to see my two grandchildren before they become teenagers.

Better to write about technical stuff than doing my head in ranting and raving about the pandemic. It seems to me things will get a lot worse before they will ever look like improving.

take care
Mike

 

[Boots in Action]

Hi @Drover,
that is what happens when you live in Melbourne and lock people up. This forum is one of the only outlets Dan Andrews hasn't found a way of banning.

As soon as we are allowed to mingle and go camping again, I won't have time to write any massive posts. Hopefully, I will be able to see my two grandchildren before they become teenagers.

Better to write about technical stuff than doing my head in ranting and raving about the pandemic. It seems to me things will get a lot worse before they will ever look like improving.

take care
Mike

It could be a looonngg few months before Christmas for Vics and NSWelshpersons @mikerezny. And the way things are going here, it might not be long before we join you in lock down of some sort. Hang in there. There is light at the end of the tunnel... somewhere in the distance. We might have time to write a few more epistles. Cheers.

 

[Drover]

Ha, my finger near fell off scrolling booties post on my phone....................

 

[Boots in Action]

Ha, my finger near fell off scrolling booties post on my phone....................

Sorry about your worn out finger! Glad you got through it all.

 

[Boots in Action]

Hi @Boots in Action,
indeed pin 2, normally reversing lights, has been hijacked for Jayco. It is intended that the existing wire on pin2 is removed and insulated.
A new wire is added to pin 2 that is connected to a permanent source of 12V in the car. This overcomes your discussion of having to leave the keys in the car, and ignition switched to accessories etc.
In my Falcon, the brake switch is basically a normal old 12V permanent in and the other side wired directly to the brake lights. There is also added switch contacts to tell the cruise control to sod off if the brake pedal is pressed.
So, the hot side of the switch has been wired back to pin 2 of the trailer socket and the brake side goes to the brake controller.

In a perfect world, Jayco would leave the 7 normal pins to perform the standard function, running all the external trailer lights, including reversing lights and electric brakes, with the earth return being used only for those items.
Pins 9 and 10 would run the fridge, and two of the three remaining heavy duty pins would be used for the 12V to the Setec AUX input to run the van lights, stove ignition, etc if no battery is fitted in the van and to charge the van battery, if fitted.
But the current wiring has been around a long time now and grew from the 7-pin days.

I like your idea of using a VSR and bypassing the Setec Aux input and its protection diode. This indeed gets a higher voltage to the van battery. A VSR is a necessity, as you pointed out to prevent the van battery being used to start the tug.

In the early day, I considered doing the same, but in the end, I wasn't all that fussed about relying on the tug to recover the battery since our 12V power usage is minimal. But in the end, I am a tight arse and I didn't want to spend the money on a VSR. I would probably have rather spent the money on a larger solar panel.

take care
Mike

Hi @mikerezny, @Drover and @jazzeddie1234 , just a quick update and change of idea from above. Tested circuits to 12 pin van plug and found that although there is van battery voltage potential across pins 8 +pos and 10 _ve, any 12 volt power applied to pin 8 is STILL connected to AUX line and through the power diode, not direct to van battery. I applied battery charger voltage directly to pin 8, and van AGM voltage rose from 13.0 volts (fully charged resting voltage) to 13.9 volts and no further. Input voltage from charger was 14.6 volts, so a loss of 0.7 volts obviously because of power diode in Aux circuit. To confirm this, I made a separate connection with 15A 7 stage charger to side of van (anderson plug) with connections directly to battery saw van battery voltage reach 14.7 volts (correct for charging AGM battery).
So no real gain other than being able to use heavier cable (AWG 8) to Aux line via pin 8 , instead of connecting through pin 2 and using the AWG 12 cabling already there. Might now have a look at changing diode in Setec for a Schottky type as only 0.2 volt forward drop compared to 0.7 volt forward drop with existing diode. May even bypass the diode altogether as van to tug wiring protected by VSR. When I get the time and inclination to remove the Setec!!!

 

[Drover]

I suppose if you were towing long distance every day and charging via tug and no solar panels yeah but spending days in camps with short drives why would you bother ginning around with it at all ????

 

[Boots in Action]

I suppose if you were towing long distance every day and charging via tug and no solar panels yeah but spending days in camps with short drives why would you bother ginning around with it at all ????

You are right on that, but I like simple upgrades on the basic electrics in my van. As no panels on van roof (and not likely to have any either!) , this mod in my own time would only be useful if at a site for a couple of days with very bad weather for solar generation, and having to move to another location nearby and have more bad weather. All I would gain would be a little extra charge into van battery whilst moving and getting maximum power/voltage to help carry any electrical loads the following day. The electrical part should pose no probs and Schottky diodes I already have. The "ginning around" would be the removal of Setec and the disconnection and re-connection of the wiring. Should help pass the time in between trips.

 

[Drover]

You are right on that, but I like simple upgrades on the basic electrics in my van. As no panels on van roof (and not likely to have any either!) , this mod in my own time would only be useful if at a site for a couple of days with very bad weather for solar generation, and having to move to another location nearby and have more bad weather. All I would gain would be a little extra charge into van battery whilst moving and getting maximum power/voltage to help carry any electrical loads the following day. The electrical part should pose no probs and Schottky diodes I already have. The "ginning around" would be the removal of Setec and the disconnection and re-connection of the wiring. Should help pass the time in between trips.

I thought it would be something like that .......................... you just have to fiddle......... I did contemplate fitting Schottky jobs on my roof panels but once I had a look at them all screwed down I went Nah.......

 

[vernonbain]

The fridge earth appears to be floating on mine, but the 7 pin continues through the aux line to the setec and to the brake circuit. Because the battery -ve must pass through the shunt, I'm assuming that all devices use a return to the setec (or shunt). Further back on mine is a chassis earth, which I think is the 240v ground.

 

[Boots in Action]

The fridge earth appears to be floating on mine, but the 7 pin continues through the aux line to the setec and to the brake circuit. Because the battery -ve must pass through the shunt, I'm assuming that all devices use a return to the setec (or shunt). Further back on mine is a chassis earth, which I think is the 240v ground.

You are talking about two types of current return here. The 240 volt circuit would be completed via the 2 wire lines (active and neutral) while the earth is for safety) from van connection to grid and also through all GPOs and 240 volt appliances in van interior. This would include the Setec as it has 240 volt charger for battery and also the fridge which has 240 volt availability too. The chassis earth is necessary to protect all persons from metal surfaces in case an active line comes loose and contacts any conducting surface.
The 12 volt circuits must have a RETURN line to complete any of the 12 volt lines from the different circuits - battery or tug lines. They are not really EARTH lines, just return wiring to complete circuits on 12 volt DC circuits. In a 7 pin circuit, the only return line from van for 12 volt DC is via pin 3 in a 7 pin plug/socket connection, or via pins 3 and also 10 on a 12 pin plug/socket connection.

 

[jazzeddie1234]

The "ginning around" would be the removal of Setec and the disconnection and re-connection of the wiring. Should help pass the time in between trips

Please post photos if you do take it apart. I have no plans to attack mine but a photo is likely to give me another idea for a mod!

 

[Boots in Action]

Please post photos if you do take it apart. I have no plans to attack mine but a photo is likely to give me another idea for a mod!

Okay @jazzeddie1234. Shall do with much care and trepidation. Did some more checking today to ensure that I don't give anybody a bum steer. The 5 large pins on the 12 pin plug on van are as follows:
Pin 8..... active line connected to VAN battery (+ve) via AUX (same line as via pin2) through diode to Setec to charge van battery.
Pin 9......for connection to TUG battery power to operate van fridge. (no connection to van battery)
Pin 10....earth return connection to TUG battery power from van fridge. (and any other electrical circuit in van)
Pin 11.....rear fog light connection using TUG power (no connection to van battery)
Pin 12.....auxiliary connection for other circuits in van but supplied by TUG power. (No connection to van battery).

Pins 9 and 10 are not used if you have separate cabling from tug to van and connections by Anderson plugs and these wires are connected directly to 12 volt fridge terminals. This arrangement would apply if a 7 pin plug/socket was used as there are no extra connections for fridge to be connected - hence separate wiring and connections to fridge.
If 12 pin socket and plug used, then pins 9 and 10 on van plug can be used to connect fridge to TUG power (alternator/battery), but with some sort of VSR or switching in line.
By not using pin 2 on van, I do not have to run a separate line to tug socket for connection to van plug and I retain the use of my reversing lights on tug. And as a result, I have to use pin 8 on van plug to direct TUG current to Setec to charge battery. But still have to reckon with the 0.7 volt loss with the power diode.
Wish me luck!!!