Installed a hitch and wiring harness on my M3

[PhilRW]

My question would be, what are the risks of dirt, water, snow etc getting under/into the space opened up in the floor pan?
Thanks

They sell a cover for it if you're concerned. I purchased one and will use it once I'm done with my next towing trip. It's a bit of a PITA to remove the ball mount adapter, but I figure I tow infrequently enough anyway.

My question is: has anyone had luck getting Tesla to enable the "Trailer Mode" toggle switch? I tried towing around a hitch-mount cargo container and the car complained "Lane Departure Avoidance limited" the whole time. That's gonna get pretty annoying over 2000 miles.

 

[android04]

DON'T DO THIS! This is actually quite dangerous; If for some reason the hitch receiver pin comes out, your whole rig will separate and the trailer complete with the ball mount will take its own path down the road. The safety chains should be connected to the hitch receiver or car. There are many reports of the pins coming out for whatever reason. Be safe.

I am fully aware of the risks and did this anyway. Like you say, there is a reason the loops to anchor the chains are on a solid, more permanent structure. However I weighed my experience and risk tolerance with what is safe and proven. Let your comment serve as a warning to anybody that might be thinking of doing what I did.

By the way, I use a receiver lock from a good brand that is not likely to fail. And I trust that the single bolt that holds the square receiver piece to the crossbar will not fail either. Maybe I'm foolish, but I'm aware of the risks. I guess I can mitigate issues from a potential failure by connecting another set of links from my welded on loop to the built in ones on the tow bar. But I should have just used the built in ones in that case. I did what I did for convenience in hooking up and removing the chains. I might still end up just cutting the welded loop on the square receiver and use the built in ones.

 

[israndy]

My question would be, what are the risks of dirt, water, snow etc getting under/into the space opened up in the floor pan?

In my experience, that hole actually helps let that stuff OUT, couldn't believe how much was up under there when I took it apart.

My question is: has anyone had luck getting Tesla to enable the "Trailer Mode" toggle switch?

Well, they have been making the Model S since 2012 and adding hitches this whole time, and they have yet to enable Trailer Mode on them, so I suspect, no.

I am fully aware of the risks and did this anyway. Like you say, there is a reason the loops to anchor the chains are on a solid, more permanent structure.

You are aware of the risk, but how about those in the oncoming traffic lane? I was thinking about adding loops until I climbed up under there and found they are provided, just impossible to reach. I got a couple of those chain links you can open and mounted them on those loops, I can hook to these more easily.

 

[ToddB]

View attachment 320377

No issues at all. Pulls my ATV and trailer like it’s not even there (1050 lbs). I was careful to make secure connections when I wired the harness. Everything is performing perfectly. I’ve recently changed the bulbs on the trailer to LED to reduce the load even thought the incandescent bulbs worked fine while they were still being used.

I do recommend getting a hitch mount with a d-ring to fasten your safety chains. My previous setup on my Dodge Challenger has the hook rings on the hitch’s main body.

Cn you provide ordering info on that hitch mount with the D ring?

 

[ToddB]

I did a few things differently on my eco hitch install on one of our Model 3's. I routed the power wire from the battery through the firewall on the passenger side, across to the driver side under the dash and installed a flush mount/push button recessed kill switch to the trailer wiring harness module. As a result, this module needs a 20 second programming when I use the hitch, which is really only a half dozen times a year. The rest of the year, the module is NOT a drain on the 12v battery. The switch is lit up when it is on, powering the trailer light module. This required finding a convenient grounding location for the switch and a placement for the kill switch. If anyone is interested in this, I can add pictures and parts ordering info. It works like a charm.

 

[israndy]

What is it you are powering? I just clipped my brake lights with a tap and ran that to the plug that I plug into my trailer. When there is no trailer, the power doesn't go anywhere.

Do you have some module that takes power all the time??

 

[oripaamoni]

I just installed the eco hitch on my sep 19 build and it has a harness behind the bumper that is capped off. Big red wire (runs to trailer pin at VC left) big brown ground and one other much smaller gauge wire. I was able to pull the connector down to the hitch area so i don't have to pull the bumper to get to it. Would have expected it to be more than 3 pins though.

 

[android04]

I just installed the eco hitch on my sep 19 build and it has a harness behind the bumper that is capped off. Big red wire (runs to trailer pin at VC left) big brown ground and one other much smaller gauge wire. I was able to pull the connector down to the hitch area so i don't have to pull the bumper to get to it. Would have expected it to be more than 3 pins though.

Apparently the smaller gauge wire is for a CAN signal. So in order to have the "official" tow mode would require a module that plugs into those three wires and outputs the trailer wiring and signals.

 

[oripaamoni]

Apparently the smaller gauge wire is for a CAN signal. So in order to have the "official" tow mode would require a module that plugs into those three wires and outputs the trailer wiring and signals.

CAN is a differential signal and requires 2 signal wires a High and Low so I am not sure it is CAN.

 

[israndy]

Oh, this is new! Someone needs to take a picture of the capped off harness.

And likely if there are 3 wires, two fat ones for power and a thin one for Can, the ground wire can be shared between the other two to complete the circuits.

 

[kevinkeenan]

Was just on the FB group trying to figure this out...

 

[Pjschae]

Was just on the FB group trying to figure this out...

I installed a hitch on my 9/19 build and saw the plug too. Pulled it down enough so that I won't have to pull the bumper to get to it. Is it usable now or do we need to wait for towing to be enabled on US models?

 

[Pjschae]

Model 3 Trailer Hitch Wiring Plug?

 

[Kiwiadventure]

Not a great idea as you now void your cars warranty.

 

[Pjschae]

Not a great idea as you now void your cars warranty.

Only voids it if the hitch is proven to be the cause of the damage.

 

[oripaamoni]

E-Bike on the electric car.

 

[yyzmxs]

[Moderator note: this post and the replies to it were merged into this thread]

Hi,

Thinking of ordering model 3 ... hitch receiver is a critical part of the vehicle for me though. Must be concealed and easy to use, meaning it must be easy to install the ball receiver. In my view it essentially disqualifies Eco (requires torquing a bolt to remove and mount the square tube which receives the external 2" piece; plus it's not a firm positive lock, rather using just a pin to mount the ball) and leaves me with Stealth which looks like a solid well designed piece of a kit.

The wiring .... which leaves me with many questions for me. I have installed hitches before on ICE cars, which has usually fuse boxes in the rear trunk and it's very simple to find fused power terminal to create a clean and nice solution, looking like an OEM. Teslas, as I learn, don't use conventional fuse boxes ... I notice that Stealth is suggesting to run a power wire all the way to the front where 12V battery is ... sounds like a medieval solution on a car like this.

I have seen a several videos, where guys installing the kits on late 2019 model 3 and all of them point to a grey looking plug, they called a trailer wiring harness. None of the people in the video have provide a detailed picture enough for me to see what sort of plug does the harness ends with. Nor have they had a need to use it, because they just used the kit for bike rack with no lights. Does anyone here know or has more information on this particular plug. Obviously, if they are correct and the plug is meant for a trailer (I assume the harness is the same for Europe, hence we in North America get it too ... (I wish the world would stop playing the silly trailer games where different rules apply around the world for the same vehicles ... sorry you will not make me buy a pick up truck or SUV in North America just to tow a couple of bikes or very light trailer) ...it would be the most elegant solution as far as wiring goes ... there is also a chance that the car could recognize there is a trailer or rack plugged in, but I think the car software would have more to say about this ...

Anyway, I am hoping someone can shed more light on the wiring harness on late 2019 model 3.

Thanks

 

[Puddles]

I have been fussing about trying to get a harness in my 3 for quite some time.

First I tried the Tekonsha clip-on as it was what was recommended on the Eco-Hitch web site. It may have worked at some point, but it does not work any more. I got all the way to a Tekonsha engineer who said "our electronics are just not smart enough to work with Tesla's wonky PWM." So I have torn all that out and started to think about a spliced system, which is terrifying as the lighting wires are so damn thin.

I did find a spot that seems great as a power tap for mid- and rear- accessories. Remove the rear seat lower cushion (2 latches along the front edge of the seat). On the right/passenger side of the battery pack... what do they call it? Penthouse? You'll see 12V taps located under a styrofoam guard/support. I ran from there to the trunk behind the side seat cushion.

I say "seems great" but... Another issue I'm having is that I decided to put a fuse block in the trunk for ease of future installs. I ran the hot terminal to the fuse block and ran the ground side to a chassis bolt back by the fuse block. It did not like this at all. When I completed the circuit to the fuse block by installing the in-line fuse, one of the sound system breakers tripped (I'm glad I had the radio on at the time) and the screen showed a scary "12 V. system problem of some sort" message. Which tells me 2 things: 1) Fuse block is completely unnecessary as the breaker will open much faster than any fuse will, and 2) There is some magic or mystery that I am not following, because I am quite sure there was no closed circuit to short out that breaker. I have the hot lead running to the isolated fuse block, and the ground lead running to a chassis bolt (and you'll notice in addition, the ground is bonded to the chassis already under the seat).

If you do trip a breaker, I found that putting the car to sleep was necessary to reset it.

But I have not really dug into it to isolate all the components and maybe I do have a short somewhere. Really don't think so.

Don't despair though, others claim to have managed to get trailer harnesses up and running. So far all I can do is stand up for what NOT to do.

 

[Puddles]

As far as the Eco Hitch, which is the one I've got, it works satisfactorily. I have my beef with the company's customer service, which I found lacking, so I generally advise to shop elsewhere, but the product itself will do what they say.

 

[yyzmxs]

Unfortunately, the fact that Tesla model 3 is such an advanced car, brings its challenges, this is one of them. We are trying to add medieval style of wiring to model 3 next generation wiring and systems. I would definitely NOT splice any OEM wires. Nor would I try to tap some unknown nodes for ground or power. The system is too smart to detect vampire draw and go into “alarmed” state.

The stealth hitch, basically relies completely on power drawn from the battery .... there should not be any issues with that. I read few reviews that it works, but I do not know for sure what module to translate turn and brake signal they exactly use. I doubt it’s their own ...

I still think Tesla will eventually offer OEM solution in North America, because they know this would happen and in the end it will hurt them .... people simply do use the vehicle to transport bikes and most people hate themn on the roof, even if it would be safe to do so. Often it is not ...

I think the evidence of the bottom cover and ready to go harness, is evidence of it. I just wish there would be more info regarding the harness.

No hitch no Tesla for me .... :-(

BTW, The EcoHitch might be OK, but the fact that you have to deal with the silly bolt which requires torquing every time I want to hide the hitch 2” square end, is just not cool. Over winter it’s ok, but in the summer, I use it once a week ... so I am used to frequently taking the ball end out. The Stealth is the right solution, kind of like most Euro cars have it. It takes 5 seconds, no wrench required. The Euro Tesla model 3 is the same way ...