Model S Trailer Hitch Installation

[Zuikkis]

Are you sure there is no trailer lights connector near the rear bumper?

Euro Refresh Model S comes with tow bar from the factory. It's not even an option, all cars have it.

US version doesn't have towing package, but it's really surprising if they have different wiring harness..

 

[drop]

The only wiring I saw in the bumper looked like it was for the ultrasonic sensors. Here's the best picture I could get.

 

[jjvan]

I did as much as I could yesterday, but I didn't know how to choose the 12V source. The '22 is much different than the pictures of the other model years I've seen here and elsewhere. There is no power liftgate module. Instead, there's an amplifier and subwoofer. I thought if I tapped into any of those wires, it could cause some noise in a speaker. Here are some photos of the area. If anyone could help me select a 12v source, I would greatly appreciate it. For anyone looking for light wiring for 2022 Model S, mine is:
Right Turn - Light Brown
Brake Lights - Purple
Left Turn - Dark Green
Tail Lights - White (light grey) - This one was hard to find because where I tapped into the wires, there's a wire for the trunk light that's also white right next to the tail light wire. The tail light wire is just slightly less white, or maybe it's the same and I just got lucky when I guessed it and tested it.

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The wiring for your 2022 Model S does look entirely different. I just logged into service.tesla.com and I can see that the electrical diagrams are totally different for 2021+. Perhaps you can log in and look at those diagrams for more information. I know they are difficult to follow though.

 

[drop]

The wiring for your 2022 Model S does look entirely different. I just logged into service.tesla.com and I can see that the electrical diagrams are totally different for 2021+. Perhaps you can log in and look at those diagrams for more information. I know they are difficult to follow though.

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Thanks for that. I had looked for the schematics, but didn't know how to find them.

 

[drop]

Does anyone know if tapping into one of the wires from the amplifier would cause a noise to come through the speaker?

 

[Zuikkis]

I looked at service.tesla.com.. it even has a tow bar "retrofit" section for 2021+ Model S. The section of interest is numbered 1230, it's not obvious to find as it is under "exterior fittings" section.

I stole some pictures from there, sorry Tesla.

The connectors under yellow tape should be there on the car harness. These pictures are from the retrofit section. They just bolt the towbar in and unroll the yellow tape and click the connectors in place.

 

[Zuikkis]

Hmm, after digging more, in the wiring harness section there's separate section for

* Harness - Body - LH (EMEA) (Remove and Replace)
* Harness - Body - LH (Remove and Replace)

"EMEA" standing for Europe, Middle-East and Asia...

Only the EMEA section mentions tow bar. So apparently it seems my assumption was incorrect and US version does have different wiring. Sorry for the trouble, just ignore my previous posts.

This must be intentional on Tesla's side, they want to make aftermarket installation difficult on markets where they don't sell tow bar themselves.

 

[drop]

I came across those pictures as well, after jjvan pointed me to the service manuals. I'm going to check that section under the bumper just in case. I would not have noticed it when I installed the hitch, since it's mostly under the body.

 

[peakay]

Can a "refresh" model x/s hithch fit the older model s or is the bolt pattern completely different??

 

[drop]

The wiring for your 2022 Model S does look entirely different. I just logged into service.tesla.com and I can see that the electrical diagrams are totally different for 2021+. Perhaps you can log in and look at those diagrams for more information. I know they are difficult to follow though.

View attachment 1009089

I ended up tapping into one of the amp wires (red) for power, after finding someone else on the forum who did that. Now I'm trying to figure out the wiring for the brakes. Your labeled picture has a left and right tail in. Are those the brakes lights? I only have one wire for the brakes, coming from the right light. What about the lights that just stay on when the headlights are on? I have found that wire in the car, but where do I hook it up on the board?

 

[drop]

So I figured out the "tail lights" are what I thought, which is the lights that turn on work the headlights. But I don't see any brake light input on your board.

 

[jjvan]

So I figured out the "tail lights" are what I thought, which is the lights that turn on work the headlights. But I don't see any brake light input on your board.

The brake lights are the same as when the both left and right turn lights are on. At least this is how it works on the older Model S. This is also how 4 pin trailer wiring works. Therefore, you connect left turn from car to left in on the board and right turn from the car to right in on the board.

Then when the brakes are applied, both the right and left lights turn on.

 

[drop]

Thanks, that makes sense. I think the issue must be that that new tail lights have separate wiring for brakes and turning. The new lights have yellow indicators, they don't just flash the brakes light. With that being the case, I don't think this board will work for the new model. Or I'm just not familiar enough with the setup to figure out how to make it work.

 

[jjvan]

Thanks, that makes sense. I think the issue must be that that new tail lights have separate wiring for brakes and turning. The new lights have yellow indicators, they don't just flash the brakes light. With that being the case, I don't think this board will work for the new model. Or I'm just not familiar enough with the setup to figure out how to make it work.

There are likely lights in the back of the car that do behave in the way the board config expects. To test, have someone push the brake and the activate the turn signals and see which lights act as both the brake and turn signal lights. For the older model S, it is the lower lights and I tapped directly into those from both sides.

 

[Zuikkis]

Red turn signals have never been legal in Europe, so here older Model S had separate (orange) turn signals and red brake lights.

If refresh MS really has orange rear turn signals even in the US, it's very likely they are now simply using the EU setup for all cars, and there simply isn't a "combined" wire available.

It can be built with relays or diodes. Just need to "or" the turn signal and brake signal, so either one will illuminate the trailer light.

 

[jjvan]

Red turn signals have never been legal in Europe, so here older Model S had separate (orange) turn signals and red brake lights.

If refresh MS really has orange rear turn signals even in the US, it's very likely they are now simply using the EU setup for all cars, and there simply isn't a "combined" wire available.

It can be built with relays or diodes. Just need to "or" the turn signal and brake signal, so either one will illuminate the trailer light.

It appears that the US version is using the orange turn signal lights. Here's a video I found showing the refresh lights:

Yes that would mean the relay board setup would need to be modified to work with the new Model S. The board I recommended has 4 relays. It may be possible to wire it up to achieve the desired output.

@drop which wires have you found from the car? brake light, tail lights, left turn and right turn? If that is the case, I think the trailer left would be logically XOR of car left in and brake in. Trailer right would be XOR of car right in and brake in.

I'll look at the relay board specs later and see if it can be set up for that.

 

[jjvan]

It appears that the US version is using the orange turn signal lights. Here's a video I found showing the refresh lights:

Yes that would mean the relay board setup would need to be modified to work with the new Model S. The board I recommended has 4 relays. It may be possible to wire it up to achieve the desired output.

@drop which wires have you found from the car? brake light, tail lights, left turn and right turn? If that is the case, I think the trailer left would be logically XOR of car left in and brake in. Trailer right would be XOR of car right in and brake in.

I'll look at the relay board specs later and see if it can be set up for that.

Here is how you would set up the 4 relays if you have the 4 inputs of tail in, brake in, left in, right in. Tail in is also known as running lights.

Note that in pre-2021 Model S, there was a left and right tail-in and they needed to be combined with another relay to get proper behaviour. Does the new Model S have a single wire for tail-in/running lights?

 

[drop]

Thank you so much. The willingness of some people to go out of their way to help a stranger on the internet still amazes me. I really appreciate the help. Over the weekend, in my frustration, I ordered the Tekonsha 119147 from Amazon for $50, after finding this thread where someone got it to work on the Model S Plaid. However, his seems to be a 2021, before they changed the tail lights, so he didn't need the red wire for brakes, since his lights don't have amber turn signals. Yesterday the Tekonsha unit arrived and I got everything to work by using the same wiring he used, except I also used the red wire for the brakes.
So I won't be able to confirm if the wiring you came up with will work 100%, but I don't see why it wouldn't. To answer your question, I was able to get proper running lights behavior with just one wire.