Trailer Connection to the Tow Vehicle

[jd1923]

Ok, so I received the new trailer plug from amazon today. I chose this Curt product (made in Taiwan, not China TG) since our Dodge OEM hitch (yes Mopar logo on the cover) on my old Ram, has the receptacle pointing right towards the hitch, instead of pointing back towards the trailer. It's always in the way of the chain hooks, as was! This plug is very short: Amazon.com: CURT 58190 Trailer-Side 7-Pin RV Blade Wiring Harness Connector, silver : Automotive

I was wiring it this afternoon and while doing so, I kept getting a 12V DC shock. Got out my voltmeter and the black wire had 12+ volts live, when NOT connected to the truck, OMG! I've installed several of these in my lifetime and I'm not at all used to ANY of the 7 wires in a trailer electrical connection being live when the truck is not attached. WTF is OTT doing? It is NOT at all standard to feed 12V DC to the truck-trailer wiring when not connected? This is crazy! hoping @John E Daviesor another member can explain (pic showing new plug). Please help!

[ScubaRx]

It appears that 12VDC is back-feeding from the battery out to the plug. Getting shocked there would mean you'd also have to be touching the ground wire, the frame or the basket as well.

@mossemi Check one of your wiring diagrams and see if the black wire from the 7-pin doesn't run directed to the battery. It probably does not currently, but I think it did in some of the earlier builds.

[mossemi]

7 hours ago, ScubaRx said:

@mossemi Check one of your wiring diagrams and see if the black wire from the 7-pin doesn't run directed to the battery. It probably does not currently, but I think it did in some of the earlier builds.

The first picture is from the 2017 Oliver LEII manual and the second is from etrailer.com.  Both indicate that the black wire is the hot/charge wire.

Mossey

 

Edited September 30, 2023 by mossemi
Typo

[Frank C]

10 hours ago, jd1923 said:

I was wiring it this afternoon and while doing so, I kept getting a 12V DC shock. Got out my voltmeter and the black wire had 12+ volts live, when NOT connected to the truck, OMG! I've installed several of these in my lifetime and I'm not at all used to ANY of the 7 wires in a trailer electrical connection being live when the truck is not attached. WTF is OTT doing? It is NOT at all standard to feed 12V DC to the truck-trailer wiring when not connected? This is crazy! hoping @John E Daviesor another member can explain (pic showing new plug). Please help!

On older Oliver trailers with lead acid batteries (before the lithium battery option availability) the black wire on the trailer 7 pin harness is the charge wire for the batteries and it IS a direct connection to the positive side of the battery bank (through a 20 amp in-line breaker, see wiring diagram).   So that wire/pin on the 7 pin trailer plug connector is energized with 12 volts from the trailer batteries, and that connection allows the trailer batteries to be charged from the tow vehicle while driving.  And it is per the SAE standard.  It worked with the old Olivers like mine with lead acid wet cell batteries because the tow vehicle alternator charging voltage was sufficient for lead acid batteries, but not with lithium batteries, so Oliver now disconnects that wire on newer trailers with lithium batteries. 

[topgun2]

1 hour ago, Frank C said:

o that wire/pin on the 7 pin trailer plug connector is energized with 12 volts from the trailer batteries, and that connection allows the trailer batteries to be charged from the tow vehicle while driving.  And it is per the SAE standard.  It worked with the old Olivers like mine with lead acid wet cell batteries because the tow vehicle alternator charging voltage was sufficient for lead acid batteries, but not with lithium batteries, so Oliver now disconnects that wire on newer trailers with lithium batteries. 

And - 

this is why in at least one video by Jason Essary (Service Manager) he recommends that owners disconnect this plug from the tow vehicle when stopped for over a few hours.  This is due to the fact that even while the tow vehicle is shut off the Oliver batteries can still draw power from the tow vehicle and, therefore deplete the tow vehicle battery.

Bill

[jd1923]

12 hours ago, ScubaRx said:

It appears that 12VDC is back-feeding from the battery out to the plug. Getting shocked there would mean you'd also have to be touching the ground wire, the frame or the basket as well.

@mossemi Check one of your wiring diagrams and see if the black wire from the 7-pin doesn't run directed to the battery. It probably does not currently, but I think it did in some of the earlier builds.

Thanks @ScubaRx for getting this discussion started! Your first thought nailed it, and yes, it's pretty hard to connect 7 stripped wires without the black touching the white or another ground! Not an easy task to wire these, especially in this extra-small plug, where the wire lengths are less than 2" long.

And thanks, @mossemi. I do understand the SAE and RV 7-way plug standards, but checkout the difference between the standards (in the eTrailer doc), where it states "Black - Battery Hot Lead" and the OTT version "Black - Battery Charge."

I've owned a horse trailer, 3 cargo trailers and 2 flatbed/car hauler trailers and have replaced the trailer plug, or socket side on the truck several times. Most of these trailers did not have their own battery. In this case, the 12V+ Black and White ground are used to power trailer accessories, like interior lighting in a cargo trailer. Here the 12 VDC hot lead is from truck to trailer, not the other direction!

And thanks @Frank C for confirming Steve's suspicion and supplying the trailer wiring diagram. Where do you get these diagrams? I have a standard OTT User Manual, in an Oliver 3-ring notebook, and a lot of now useless warranty information in a zipped case. I do not have the Oliver trailer connection graphic, that Mossey showed above, and I certainly do not have ANY schematics! Every time I see a wiring or plumbing diagram, in one of these posts, I save a copy to my Oliver folder.

[jd1923]

4 hours ago, topgun2 said:

And - this is why in at least one video by Jason Essary (Service Manager) he recommends that owners disconnect this plug from the tow vehicle when stopped for over a few hours.  This is due to the fact that even while the tow vehicle is shut off the Oliver batteries can still draw power from the tow vehicle and, therefore deplete the tow vehicle battery. Bill

Thanks Bill @topgun2 too! Now I have an issue. Yes, I have the four 6V golf cart style lead acid batteries, but I also have ample solar wattage to charge these! 

I never want to charge these large AH capacity trailer batteries from my truck alternator when driving, nor possibly drawing current from my truck batteries when sitting. Last thing I need is alternator or truck battery charging issues. I need to disconnect this Black 12V+ lead. Also, I'm not going to get in the practice of disconnecting the trailer plug, unless I am disconnecting the trailer. This is crazy! Good thing OTT stopped doing this.

I can simply disconnect it at the trailer connection plug but would rather disconnect it at the battery side. Anybody know where the 20A breaker is located, as shown in the wiring diagram that @Frank C supplied?

[Frank C]

13 minutes ago, jd1923 said:

Thanks Bill @topgun2 too! Now I have an issue. Yes, I have the four 6V golf cart style lead acid batteries, but I also have ample solar wattage to charge these! 

I never want to charge these large AH capacity trailer batteries from my truck alternator when driving, nor possibly drawing current from my truck batteries when sitting. Last thing I need is alternator or truck battery charging issues. I need to disconnect this Black 12V+ lead. Also, I'm not going to get in the practice of disconnecting the trailer plug, unless I am disconnecting the trailer. This is crazy! Good thing OTT stopped doing this.

I can simply disconnect it at the trailer connection plug but would rather disconnect it at the battery side. Anybody know where the 20A breaker is located, as shown in the wiring diagram that @Frank C supplied?

On my Elite II, the 20 amp breaker is under the street side bed. It’s covered by a red rubber cover.  It’s a self resetting breaker, but you can disconnect the black wire that comes from the 7 pin harness.  And I get all the electrical/plumbing diagrams from the Oliver university resource on this website.  It has manuals by year for the trailers. 

[topgun2]

37 minutes ago, jd1923 said:

Good thing OTT stopped doing this.

As far as I know - OTT only stopped doing this for those trailers equipped with lithium batteries.

Bill

[jd1923]

24 minutes ago, Frank C said:

On my Elite II, the 20 amp breaker is under the street side bed. It’s covered by a red rubber cover.  It’s a self resetting breaker, but you can disconnect the black wire that comes from the 7 pin harness.  And I get all the electrical/plumbing diagrams from the Oliver university resource on this website.  It has manuals by year for the trailers. 

Thank you very much, Frank! I'll look for this today, disconnect the black wire, and then test at the trailer plug. If I do it right, the black at the trailer end should show an open circuit and no more 12V+.

Being only 3-4 months into OTT ownership, we're learning every day! I will look for these online and it would be much better to have electronic PDF searchable manuals than a folder full of paper.

[jd1923]

30 minutes ago, topgun2 said:

As far as I know - OTT only stopped doing this for those trailers equipped with lithium batteries. Bill

Likely in recent years, the OTT lithium upgrade means solar upgrade too. Back in the day when many TTs and RVs had only 1 or 2 "marine" style batteries, and no solar, charging from the truck while driving made sense. You could drive to your next destination and have recharged house batteries.

Lithium or not, I would not want to have 4 large AH under charged lead acid batteries, powering an inverter when boondocking overnight, and then leaving early in the morning, solar not having enough time to recharge. This would put an enormous current draw on the truck charging system which could cause ignition or computer sensor failures. BTW, this 12GA wire is not rated to charge a half-charged 300+ AH battery bank and could overheat and cause fire. This 12V+ Black lead must be disconnected on any trailer that has an inverter with a large capacity battery bank. With all your help, mine should be disconnected asap, thank you. I'm certainly glad my trailer plug needed replacing, which allowed me to learn this today.

[jd1923]

Thank you @ScubaRx!!!

I opened this new discussion and asked the moderators to move a half dozen posts here, vs a Mechanical & Technical Tips thread I started on Suspension and Brakes Maintenance. Hopefully, @mossemi, @Frank C and @topgun2 who helped me immensely will find the new location.

[jd1923]

The setup under the streetside bed on our 2016 Hull #113 is quite a bit different from @Frank C's. Perhaps Frank, with hull 461 does not have solar? My pics attached below.

I do not have the 20A breaker described before. I have a similar 12V+ bus connected on the ground side to a 40A breaker. The red cable far lefty appears to be the battery hot lead, the one far right connects to the breaker and to ground further to the right.

Look close at the bus pic and you will see a smaller gauge black wire disconnected. Thanks Frank, I got lucky, disconnected this wire and it is the 12V+ going to the trailer plug.

Anybody know what the other wires are? Mainly interested in the 3 black wires that have built-in disconnects. Also like to know what the red and green wires are. The large red marine switch does what? I turn it and nothing apparent! I would think it opens (disconnects) connection to the battery bank but switch it off and not much happens! There should be a main battery cutoff switch! 🙃

[Steph and Dud B]

@jd1923 that is perfectly normal wiring. Our previous trailers all had that wire hot to the batteries. (As others have said, it is not that way with our lithiums.) We even made a jumper plug to connect that terminal to the running lights so we could leave the running lights on if we had to leave the trailer on the side of the road at night because of a breakdown. You might see some campers leave their trailers lit that way in campgrounds, too. Kinda a newbie thing.

[MobileJoy]

In my 2021 OEII, there is a red switch like the one pictured above, but it is located in the upper street side cabinet near the pantry and right near the Zamp solar controller. That switch breaks the power connection between the solar panels and the controller. The switch in your photo (being so close to the Blue Sky box) might do the same. The switch is useful  when disconnecting battery cables so they are not carrying charge while disconnected.

[Frank C]

9 hours ago, jd1923 said:

 

Anybody know what the other wires are? Mainly interested in the 3 black wires that have built-in disconnects. 

The three black wires with the large yellow fuse holders are the 12 volt hot leads for the three stabilizer jacks.   On mine they are labeled for a 30 amp fuse.  And on most Ollies (including mine) the front jack has another redundant fuse holder located at the jack itself.  And you are correct that I have no solar panels on my Ollie.  But if you look in my earlier post of my street side bed wiring, you'll notice the coils of heavy gauge red and black wire.  At that time (and maybe still now) Oliver was installing the heavy gauge wiring for the solar package, even if the solar panel option was not installed.   So the wiring is in place between the hulls from the roof down to the street side bed so the panels can be added in the future if desired.   I use a Zamp portable solar panel setup instead connected to a Zamp port that I installed.

[Rivernerd]

I note that the spade terminal on one of the black wires is not connected to the screw above it.  Is this intentional?

[topgun2]

12 hours ago, jd1923 said:

Look close at the bus pic and you will see a smaller gauge black wire disconnected. Thanks Frank, I got lucky, disconnected this wire and it is the 12V+ going to the trailer plug.

Rivernerd - 

As per the quote by jd1923 above.

Bill

[jd1923]

1 hour ago, Rivernerd said:

I note that the spade terminal on one of the black wires is not connected to the screw above it.  Is this intentional?

Yes, it's now taped up and pushed below. That is the 12V+ to the front trailer connection that I just disconnected on purpose.

[jd1923]

13 hours ago, Steph and Dud B said:

@jd1923 that is perfectly normal wiring. Our previous trailers all had that wire hot to the batteries... We even made a jumper plug to connect that terminal to the running lights so we could leave the running lights on if we had to leave the trailer on the side of the road at night because of a breakdown.

Thanks @Steph and Dud B that's a good idea for safety needs. Maybe I can run a switch for this purpose. Mine will stay disconnected, since I do not want charge going to or from the TV at all. 

I'm realizing that most of you have past experiences with travel trailers. We do not. Owned a Class A and a Class C RV, but not travel trailers. The 6 trailers I've owned never had batteries (except the small one for the brakes safety disconnect switch). When there are no house batteries, the 12V+ is used to tap the TV batteries to power for example cargo trailer interior lights. Then when the trailer plug is disconnected, there is no power at the plug.

[jd1923]

6 hours ago, Frank C said:

The three black wires with the large yellow fuse holders are the 12 volt hot leads for the three stabilizer jacks.   

Thanks @Frank C this makes sense and yes, the front jack has the same yellow fused link (I have pulled off that jack head for servicing). 

And thank you @MobileJoy the solar cutoff makes sense right there. I'll test mine to make sure at some point. Turn it off and the display should show 0 amps incoming. Why isn't there a battery cutoff on these OTTs? (or is there)

[John E Davies]

https://olivertraveltrailers.com/forums/topic/2688-how-to-junction-box-for-trailer-harness-repair-or-extend-the-harness/

You will have to install your own cutoff switch, these early trailers certainly have none.

BTW, I would NEVER recommend a 7 pin plug or receptacle with a steel housing. The inside will inevitably rust, short out the terminals, cause weird light problems and blow fuses, use a plastic housing only! Living in Arizona makes this much worse, the red dust is up to three percent iron oxide, and highly conductive when you add a little moisture.

John Davies

Spokane WA

[jd1923]

3 hours ago, John E Davies said:

BTW, I would NEVER recommend a 7-pin plug or receptacle with a steel housing...

John, thanks for the link and yeah, I get it and thought some about that. I really thought the metal would be better in the SW and worse anywhere north where they salt the roads!

I purchased this because it is 2" shorter than all the plastic ones. My receptacle runs in parallel to the bumper and the end of the plug goes over the hole where you mount the chains. Bad design, but it's there unless I change everything. I did run electrical tape around everything inside, about 3 layers of tape between wiring and the metal housing. I will buy a backup plastic one.

Anybody know of a short plastic bodied plug? Or a 90-degree trailer plug?

Edited October 2, 2023 by jd1923
added last line

[jd1923]

@John E Davies made a good point. A quality rubberized plastic casing would be preferable, as long as the copper blades remain in good condition. Mine were toast! Hoping my new metal-cased plug lasts as long as the internals. I’ll apply dielectric grease around the plug so that dust and water will not affect the terminals.

Take a look at my pic. This Mopar hitch has a housing for the trailer plug receptacle welded to the hitch in the 90-degree direction. It would be difficult to change this. There is 4 ½ inches clearance to the eyelet for the safety chains and 7” total to the 2” receiver. The standard plastic trailer is so long, I struggled every time, connecting and disconnecting. Now I have 2” extra room with this metal shorty! Tested all circuits today and all is good. Thanks

[ScubaRx]

On 10/2/2023 at 7:18 AM, Frank C said:

...At that time (and maybe still now) Oliver was installing the heavy gauge wiring for the solar package, even if the solar panel option was not installed.   So the wiring is in place between the hulls from the roof down to the street side bed so the panels can be added in the future if desired...

Oliver quit pre-wiring the trailers for solar several years ago. The mounting plates for the panels are still fiber-glassed, into the roof however.