Curt Class III 13256 on Canadian 2006 XLE Limited AWD (with pics)

[robaer]

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...

[robaer]

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).

[topspy]

Nice job, pics, & write-up!! 8)

[robaer]

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.

[robaer]

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

[topspy]

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.... 8)

[jh818]

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

[robaer]

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)

[brian_bp]

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...

... 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.

[robaer]

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__light...apter_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.

[brian_bp]

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.

[brian_bp]

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.

[robaer]

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.

[brian_bp]

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.

[robaer]

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.