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Discussion Starter · #1 ·
I added to this thread (http://siennachat.com/forum/index.php/topic,16.0.html) that I would be documenting the installation of a trailer hitch and wiring on my recently purchased 2006 XLE Limited AWD van.

I chose the Curt 13256 as it appeared to offer the better look and clearance from various threads I read... I will also be installing a full 7 Blade towing adapter to power things (and likely a Prodigy braking system at a later date). I decided to share my experiences, pics and lessons learned in routing wires etc to accomplish this. Along the way I will provide an inventory of parts used and give you an idea (in CDN$) of my costs to complete for others foolish (Canadian for hardy) enough to DIY.

So to start... the attaching of the hitch itself.

I bought the hitch over the web and had it shipped from Toronto to Winnipeg. Cost was $226 including taxes and shipping and that was from redtrailers.com.

It arrived and THEN I discovered that the threads of the nuts in the frame were heavily rusted (should have looked under there before buying the hitch). I believe the previous owner removed the tie downs or trailer hitch at an early date and 3 years of Canadian weather had done its thing. The van itself is very clean of rust... but those nuts were not properly coated and were toast. Rather than strip bolts and brake knuckles, I decided to take it to a local mechanic to have him retap the threads. They did this for ~$50 (which I thought was pricey but the nuts were heavily corroded).... however they only did 4 of the 6 nuts. The 4 nuts they did do were smooth as silk and I was able to apply the required 64 Ft-lbs of torque and without any problem... good as new. Will be taking the van into the mechanic to re-tap the remaining 2 threads but first i am going to see if I can find an M12x1.25 die and tap set to do it myself... (I have rethreaded smaller nuts before on home projects and it wouldnt be the first time I needed an excuse to buy more tools)

I should have had them mount the hitch but I really wanted that DIY satisfaction and decided to just have them do the tapping for me.

After I got the van home, it took about 25 minutes. Like others I had to move the muffler out of the way with a 2x4 wedge and it gave me enough access to bolt in the 2 bolts (the third will likely be accessible too... in this manner). I could have taken the rubber muffler bracket off (the Curt hitch included instructions on how to do this with an open face wrench and screwdriver pry bar) but wanted to try this way first since I thought most who followed would do the same. I used a fixed jack to hold one side of the receiver up while I loosely bolted the other side first.. I tightened everything up with a torque wrench after the bolts were all in (at least the 4 I could). Unlike others... I didn't need to jack the van up onto a ramp to do this. I found it quite easy to lie under the back with safety glasses on and just hold the receiver in place with my shoulder (and chin). If it had been higher I think I actually would have had a harder time holding it in place.

Here are pics of the install...
 

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Discussion Starter · #2 ·
Once installed... the curt snugged right up tight to the black part of the bumper.. there is about 1 mm (<1/8 inch) clearance if that. It looks great (imho) and fit like a dream. In the following pics you will see that receiver with this tight clearance, but when you look under the van on each side it has plenty of clearance from the rear seat well and muffler area. You will also see I added an after market chrome hitch cover ($6 at Princess Auto) to keep debris out of the receiver (although the back is still open so i might pop a cap in it too).
 

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Nice job, pics, & write-up!! :D 8)
 

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Discussion Starter · #4 ·
Part 2 of the install... hitch is now fully installed.

I ended up rethreading the nuts myself. The M12x1.25 is a rare thread size and rather than order in a special tap and die to do this, I figured I would first try using some WD40 and a 1/2 inch round wire bristle (bought from plumbing section of local hardware store for $5) and some elbow grease. I also decided to uncouple the rubber mount for the muffler this time as the 3rd bolt on that side would be tough to work on with the muffler only partially out of the way.

It took about 90 minutes to get the bolts in. I basically worked the bolts in a bit at a time... removing them periodically to clean and re-reclean the hole. A real pain but it worked. Torqued all the bolts in place and hitch is now good to haul. On to the wiring...

Here's the supplies I bought (I had some of these in my shop already, but decided I wanted to overkill the wiring approach and borrowed some great ideas from this group about how many wires to run back from the battery etc...) attached are some pics as I started.

I am running a dedicated ground wire to the back (based on some good comments from zero260 I believe) along with +12V. 10 Gauge heavy jacketed cable. One +12 is going to feed the Modulite for the basic trailer circuits as well as the reverse light circuit. The other is dedicated to the +12V output on the 7blade. Relays will be used for the reverse and power feeds.

Both hot wires are using 30Amp self reseting circuit breakers (in place of fuses) and those will be mounted in the engine compartment.

I decided to mount all the junctions in a dedicated box to contain all the relays and couplings. The modulite will mount to the surface and since I want to be able to manually disable the +12V from being live (ie not just with the relay that ensures its only on when the ACC or Ignition is on... but also kill it all together should I just not want that circuit live at all.

In the jack compartment, looking towards the wheel well, I found a mounting hole and enough space for 5x5x2 electrical box. I will place the relays in there, feed both the power lines from the front and the hitch cable from the back through 2 large ports and I decided to also run the modulite wiring into this box for its couplings to also be protected.
 

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Discussion Starter · #5 ·
Part III
For the actual harness, I decided to build a cable bundle (instead of run individuals lines and twist tie them). I cut the various connectors and adapters off the wiring harness as it came (ie it provided a nice 4 wire connector so you could just upgrade an existing system without having to splice). I spliced in new 12 and 14 gauge wires where appropriate and soldered the connections, covering each joint with heat shrink tubing. I wrapped all 7 wires in 7 feet of wire sheild (corrugated plastic wire covering... see photo) and then for about 4 feet of the harness that is exposed to the outside, put on heavy duty shrink wrap (that had a criss cross pattern for looks and better protection). This also water proofs the cabling better should any of my soldered splices get exposed.

I will run this cabling tomorrow, but wanted to do both the battery compartment wiring and harness together... so I now proceeded with the box wiring... planning the layout of components etc. I prewired as much as I could now and will make the actual connections to the harness and feed wires once I have run those on the vehicle and in place.

I did discover something interesting in doing tests on my bench first though...

I wired up a bunch of 12V lights and feed some power to the rig and tested each circuit to make sure I didnt cross a wire anywhere (better here than in the car after getting it all installed). When testing the reverse light circuit.. I noticed I was getting a "flicker" on the tail lights as I disengaged the power to that circuit (it was very minute and if I didnt have the meter connected at the same time. I actually might have missed it). It was like the relay was bleeding for a millisecond and causing the modulite to spike the tail light and turn signals. Thinking I needed to insert some diodes I carried on and noticed that when testing the dedicated 12V circuit... it did NOT cause the modulite to flicker... which is strange since at this point they are technically the exact same type of circuit.

So now I assumed the problem was a bad relay on the Reverse light circuit so I swapped it out... same problem. Then I thought the socket the relay is plugged into (although thats really weird to be cause of something like this) and replaced it... still had the problem.

The only difference between the +12v and the reverse light circuits is that the +12v had a switch on the relay side so I could disable that signal if I wanted to override the system. This switch is grounded. I discovered that when I removed the ground from the swith... this circuit would also cause the modulite to send a flash as well. re-grounded the switch.. that circuit stopped causing the bleed. I guess the switch I bought has some sort of diode function or is keeping the circuit from spiking in some way.

Its possible these symptoms wont show up in the actual vehicle because in testing I am applying a sudden and hard 12V to the relay for testing whereas the actual circuit in the car is coming from the reverse lights OR the rear ACC circuits that are likely lower amps etc... but to play it safe I am going to add a second switch so I can disable the reverse lights as well (which isnt a bad Idea since that purple wire is not always used for just reverse lights... I have heard differing opinions about that connection so this way if I ever encounter a trailer that wants it to be something other than reverse lights... I can just disable the circuit and not interfere with that).

Tomorrow I should be able to install it all...




When I tested the reverse light
 

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Hmmmm....I'm definitely NOT an expert on all of this, but it looks to me like you could actually even make a living at doing this if you wanted to.... :D 8)
 

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Wow! Looks like you're installing wiring for a room addition or something. Just like the DIY Network...Bob Villa.
 

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Discussion Starter · #8 ·
Yea... I decided to over-do this one... love hobby projects like this and from reading other posts, I knew I would have a discerning audience to review it.
I mounted the external connector to the hitch last night and wired it up along with the modulites 2 signals, stop and tail connections. Will provide some pics when I get the battery line run. It was a 30 minute job if that... Were it not for the extra +12V ACC and Reverse light circuits... I would be done.

I have an outstanding question on the mobile electronics thread about the best place to tap into the ACC and Reverse light circuits (to drive the 2 relays I have for those needs). I also realized that my modulite would be powered from the battery and therefore would be "live" 24/7. While the lights on the trailer would not be on (because the van lights would go off at some point once the key was out of the ignition) I wasn't sure if this is normal or if I should change that power source to an ACC based curcuit up front (leaving the +12V ACC line itself on the battery since the relay and switch in the back kills it after key out)
 

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I will admit to not have read every word or examined every bit of every photo of the installation, but I agree that it is nicely described and an exceptionally nice installation. Now I'm embarrased to show photos of mine... :-[

robaer said:
... since that purple wire is not always used for just reverse lights...
Purple? That's unusual colour coding - there is no purple wire in the common trailer wiring configurations. Of course electricity doesn't care about insulation colour so it doesn't matter as long as the correct pin is used... which would be the centre (round) pin of the RV-type 7-pin connector, which is the "auxiliary" connection for whatever use is desired.

The auxiliary connection may also be used for a separate stop (brake) signal, or even to run a rear fog lamp, so I agree that a switch to disable it is appropriate.
 

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Discussion Starter · #10 ·
Yes, you are correct.. I was being sloppy in my reference to the wire colour instead of referring to its pin out.

It is the center pin of the 7 blade plug. I see that the Green, Yellow, Brown, White and Black choices of wire colour in trailer wiring are pretty consistent... even the choice of Blue for powered brakes seems industry wide. When it comes to that center pin of the 7 blade however... there seems to be differing references. In many systems where its referenced as "AUXILIARY" its often shown as an Orange wire but other wiring diagrams I have tripped over can also show it as Purple (and they refer to it as "Backup Lights" or "Hydrolic Power"). Since I am more likely to use it for backup lights than whatever AUX is... I chose to use the center pin for reverse lighting (and hence called it purple for short)

Here is a common reference diagram I have seen several sites refer to..
http://www.etrailer.com/faq-wiring.aspx

I loved the idea of this multi-tow (http://store.uhaul.com/Wiring__lights/Moving/Multi-Tow__Adapter_7_to_7_4) and found it at Uhaul for $35 CDN locally too. Its center pin is wired with a purple wire so that got me on the bandwagon I guess.

Is there is no ISO standard like many other wiring interfaces... Will have to dig into it sometime to figure out.
 

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robaer said:
Is there is no ISO standard like many other wiring interfaces... Will have to dig into it sometime to figure out.
True. There are SAE standards for other towing interfaces, but apparently not for the RV-style 7-way.
  • SAE J1239 - 4 to 6 pin connectors
  • SAE J560 - 7-pin connector
  • SAE J1067 - cable

Many of the type of automotive standards which are managed by ISO for Europe are handled by SAE for North America.

  • ISO 11446 13-pole towing connector
  • ISO 1724 - 12N connector (primary towing, lights)
  • ISO 3732 - 12S connector (supplemental towing)
None of these ISO standards are followed here.

The linked eTrailer diagram shows SAEJ1239/J560 colour coding, but applies it to the RV connector (which normally does not use the same colour assignment) and invents a purple-for-backup extension of the scheme (because the yellow for aux was already taken for left turn). Most diagrams published on the web - other than those copied from the same source as eTrailer - show the conventional RV assignment.
 

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robaer said:
Since I am more likely to use it for backup lights than whatever AUX is... I chose to use the center pin for reverse lighting...
Since AUX just means any auxiliary application (anything in addition to the basic functions), reverse lighting is a perfectly reasonable (and common) use.
 

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Discussion Starter · #13 ·
Thanks... saved me the research on SAE/ISO standards... relieved that they exist too.

Good point about the AUX use. I was thinking about "auxillary power" or something like that where its a second feed of switched ACC for something where you want 2 circuits coming off the battery (the usual +12 and this line as well). Hooking it to reverse lights for that purpose would fail... but since its likely intended to identify this pin as being for any auxillary application for you to decide... than it does fit nicely.

I didn't go back and look at the link... but as long as the "RV PLUG" pinouts (for lack of better word) line up with the J560 than I don't care about colour inside the van. If they mismatch then I am concerned and would likely change my wiring to confirm to the J560 since I have always preferred wiring to a standard and doing "cross wiring" if the application requires a different pin out on the receiving end. that way I can always go back to spec when something stops working and not second guess what pins I used for what (and not try to remember which flavor of standard I followed). I believe you indicate in your post that it does indeed match the J560 for pinout locations so I am happy.
 

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SAE J560 actually descibes the connector with 7 round pins, which is used on commercial trucks. The RV-style connector which we use for our travel trailers has flat pins (except the centre one) and is mechanically incompatible; there seems to be no SAE standard for it, and the normal pin assignment doesn't correspond to the J560 configuration. The eTrailer diagram for the RV-style 7-pin does match normal practice for the pin functional assignment, despite the weird colours.
 

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Discussion Starter · #15 ·
Thanks... really good info for me.

I will stick with it as wired then. Interesting they dont have a standard given how many of these RV plugs are out there and how the typical user would just "plug it in". Imagine the trailers +12V ACC circuit getting fed only when you turned left because that trailer manufacturer decided to use some proprietary configuration.... or if the signal lights on the van controlled the backup lights... lol...while unlikely its possible without a compliant standard to refer to at time of sale.
 

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Discussion Starter · #16 ·
Part IV - running the mains to the battery

I started in the back jack compartment. I hooked the 10/3 cable up inside the box and added a coil of blue 14 Guage wire for the line that will go into the cabin for the braking system to connect to. I fed this wire down through a rubber grommet in the bottom of the jack compartment. You can see it in pic 1 from underneath. This comes out just above and to the left of the tailpipe, so I snake it by the muffler hanger bracket, over the suspension coils and along the frame on the passenger side. You will note in the second picture that I used a couple of insulated brackets to secure the wire and the orangish goo is anti-corrosion gel to make sure rust wont set in to where I drilled the frame for the screws. Mostly I just zip tied the cable to existing brackets though... pretty easy.

Once at the engine compartment, I snaked the cable up into the engine following as close to the passenger compartment as possible. In the 5th pic you will see the blue brake wire has now been seperated from the black 10/3 cable so i can feed it into the passenger compartment at some point for the braking system. The 10/3 then snakes over the top of the engine by zip ties to an existing wiring harness that is hidden up inside the top area by the dash.

I dont have the circuit breakers installed yet, so I have just neatly tucked the cable around where it will eventually end up. The cb's will be mounted on angle bracket just to the upper left of the engine compartment... 3 of them. Two for the two 12v lines going back to power my relays and modulite and one for the brake system power that will be in the passenger compartment area at some point.

I got lucky... I bought 20 feet of 10/3 even though I estimated I would only need 15 feet to run the line. But I needed all 20 feet. There was non to spare. Also, the 10 guage wire and insulated jacket was fairly flexible... but if you just rung some 12 or 14 Guage you could save some time and hassle in doing the wiring and likely be no worse off. 10 Gauge is likely overkill... but it looks good.

In the back, I made sure I had about a 14 inches of cable inside the jack compartment so I could remove the trailer wiring box if I needed to do some work (ie replace a relay or something someday).

I also ran the wiring that is going to feed the modulite with signals, tail and stop lights. I basically did exactly what is shown in the e-trailer video for installing the wiring harness so I wont repeat that activity here. Same for attaching the 7 blade to the hitch and snaking those wires to the jack compartment... it went up through a grommet in the rear seat well and under the carpet to the compartment with ease.
 

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Discussion Starter · #17 ·
Part V - Wiring up the harness and mounting the box into the jack compartment.

Here I show the wiring of the harness (from the 7 Blade) to the box. I used crimp connectors with male/female connections so I can remove the harness someday if needed. Easier than cutting wires and leaving not enough to work with next time.

In the first pic you can see where the 10/3 line and brake wire go through the rubber grommet in the bottom of this well. In the second pic you can see I removed the 2 bolts that hold the jack holder so that I had more room to stick my hands in there.

The design I chose actually didnt require removing the rear panel to get access...although that would have made bolting the box a bit easier. My hands got a couple of scratches trying to hold bolts and nuts in place as I tightened them... but there was just enough clearance for a small ratchet to fit in and tighten them down.

Pics 4, 5 and 6 show the finished product. The hose just above the box in pic 5 is drain hose from the compartment above. It just pulls out of the hole in the body and makes it easier to get your hands in there... and then it just inserts back into that hole. Toyota did a nice job of keeping water out of areas that it could pool... and it protects my circuit box too. In the 6th pic you can see the red and blue switches. The blue disables the center pin on the 7 blade (which is my reverse lights in this case) should I have a trailer that expects this AUX line to be something else. The Red switch disables the +12v relay so that I can manually cut off power if I dont want something running on the trailer from that line. Both are lighted switches (though very dim) and easy to reach without removing the jack.

The last 2 pics show the 7 Blade mounted to the curt hitch receiver... I think it looks great... tidy and easy to access. I also really like that multi connector as it gives both 4 and 7 wire out... most trailers just want the 4 and it saves me hauling a 7->4 adapter around.
 

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Discussion Starter · #18 ·
Part VI - building and installing the housing for the circuit breakers

I was going to mount my 3 circuit breakers (40 Amp for +12V dedicated ACC line, 30 Amp for Modulite trailer lighting circuit and reverse light circuit and 20 Amp for the braking system which is yet to be bought) onto a piece of angle iron and bolt that somewhere in the engine compartment. On the weekend I planned to do this, I also happened to be repairing my outdoor plugs and had an idea. The 90 degree PVC housing/junction box was about the same width internally as the CB's I had. It was deep enough to house the 10 Gauge wiring and connections and long enough to hold 4 or 5 CB's along its length. I took it to the engine compartment and discovered that the place I wanted to mount the CB's (upper right corner just above the large fuse block) was too narrow to fit it in. BUT, I could cut and section the box to be just wide enough for the 3 CB's and rebond it together with PVC glue. I could also reduce the length of the goose neck openings (particularly since I only needed 1)... and I thought it would be fun too.

So... later in the week I set about doing just that. I ended up only putting the 2 CB's into the compartment that I need right now (ie left out the one for the brake system) because after building the box, I found a better solution for this. I happened to stumble across some ATC blade CB's (ie, they are similar to a normal car fuse but its a Circuit Breaker instead) and in looking on the web for a small fuse block I could use instead of my Frankenstein pvc thing (plus it would allow me to switch out a bad CB with even a fuse should I burn one out or something) I found the perfect little block. I likely wont get it for a couple of weeks but since the cable lengths and location wont change... I decided to go ahead and proceed with the original plan for now. Here's some pics.

I haven't connected the hot feed to the battery yet... want to test everything one last time and will just alligator clip it for the tests... and it was getting late... but the stuff is all mounted now.
 

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Discussion Starter · #19 ·
Part VII - Final Chapter - hooking into rear ACC+ and reverse lights line.

So, with the mains powered up at the front and one line running through a relay at the back, the signals for right, stop, left, and tail lights connected to the modulite and the 7 blade wiring harness permanently attached, all that remained was to tap into a switched ACC source (so the modulite would operate when the key was in the ignition) and tap into the backup lighting circuit for that pin on the connector.

For the ACC+ I decided to use the driver rear corner panel connection for the 12V plug (aka "cigarette lighter plug"). I had noticed the 120V plug back there and mentioned this in earlier posts but had completely overlooked the round 12V plug which is only on when the key is on. Perfect.



That was an easy solution as it just meant running the wire from the rear left compartment, under the carpet and up behind the subwoofer. Popping off the rear panel was straight forward and very similar to what you see in the youtube videos for connecting to the drivers side lights. I had to pop more of the panel off (ie pulling it away from frame) so that I could reach the center wire on the plug and tap into that... but it pulled off freely and no plastic grommets broke.

To connect to the backup circuit, I mentioned that I was going to tap into the red with black strip wire that runs from the drivers side kick panel, along the drivers side door plates (front and back) and then into the rear quarter panel. When I removed the kickplate for the rear door (simple pry up and out maneuver with my fingers) I was pleasantly surprised to find the wiring harness had places where it was opened up and covered by clear accessable panels. This meant I could easily tap into the circuit under one of these access points and not have to open the harness and sort through wires.

I had to remove the rear door cable guide that covered the rearmost of these clear access panels (see pics below... easier to see than describe) and easily found the red with black stripe wire. I tapped into it with a T connector and did a quick test by using a circuit tester while the car was in reverse... all good.

Closed everything back up and my trailer harness was now completely wired.



Next project will include installing the brake system (already have the wire going from the rear of the van to the engine compartment... so mainly installing Circuit Breaker and brake system unit in cabin). I also would like to install bags in the coils to help support heavier trailer loads. Since my trailer needs right now do not require assisted braking or air bag support... I am leaving those 2 projects to maybe next year.
 

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Hi Robaer,

I'm in the process of acquiring all the components for my 2007 Sienna to start towing. I am impressed with your set up....and would love to have something close to it on my Sienna. I am fairly ignorant when it comes to electronics and all your explanations, while in-depth, get my head spinning. I've narrowed down the parts I'm going to buy. I'm going to buy the Curt 13256 hitch, the wiring harness and the hopkins multi tow 7-pin/4-pin adapter. I guess my question is how is the Hopkins multi tow adapter mounted on the hitch frame? do I need to buy a housing box as well? Or is a clamp included in the kit? Thanks in advance for your help.

Chad Mochrie
Burbank, CA
 
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