Trailer hitch on 2021 refresh?

[leecox]

This looks great! But I don't think there's any wiring at all to tap into. That's likely a "new build" thing. That blue wire harness simply doesn't exist on the older cars. (Mine is an October 2021 Refresh LR ...)

Yeah, it may very well be. There is a wiring hitch harness though. The orderable harness might only go from the module with the heatsink to the plug and the real hitch harness might be in the LH Body harness for the new cars. IDK, I've asked my local service center for the part.

 

[dmurphy]

Yeah, it may very well be. There is a wiring hitch harness though. The orderable harness might only go from the module with the heatsink to the plug and the real hitch harness might be in the LH Body harness for the new cars. IDK, I've asked my local service center for the part.

Right, that's what I'd expect. Very similar to how it works on the X - the hitch "harness" goes to a connector mounted behind the rear crash bar/hitch bar. That connector then goes up to one of the body controllers... that's what I think is missing on the 'early' refresh cars - the wiring from the body controller to center-of-rear-bumper.

 

[leecox]

Yeah, and replacing the LH Body Harness is no joke. Also, due to the differences between the years it may not work to order just that to change it over.

There is a LOT it connects to, just like the main harness on other cars. One could theoretically order this harness with the Hitch components in it, then strip out the hitch components and retrofit them into an earlier harness as long as the pin placement for the body controller was 1. There, IE the pin exists on our controllers. 2. Wasn't occupied by another pin/use. It's making your own jumper harness out of the factory part (that isn't cheap).

But that's a lot of effort to get a factory hitch. I'd rather go the 3rd Party route.

 

[leecox]

Following up on this after further research. There are 6 different harnesses for the LHD cars and the LH Body Harness:

#	Part Name	Part Number	Sales Restriction	Repair Quantity	Order in Quantity
1	ASY,HARN,MS,LEFT HAND BODY,LEFT HAND DRIVE	2486394-00-C	Over The Counter	1	1
1	HARN,BODY,LEFT,MS,DRLEFT HAND,ALL,TW01	2486394-01-C	Over The Counter	1	1
1	HARN,BODY,LEFT,MS,DRLEFT HAND,ALL,TW01	2486394-71-C	Over The Counter	1	1
1	ASY,HARN,MS,LEFT HAND BODY,LEFT HAND DRIVE	2486394-00-D	Over The Counter	1	1
1	HARN,BODY,LEFT,MS,DRLEFT HAND,ALL,TW01	2486394-01-D	Over The Counter	1	1
1	ASY,HARN,MS,LH BODY,LHD,NA,PERF Can replace 3486394-00-B, 3486394-01-B. For Canada Use: 3486394-01-B + Ferrite	3486394-01-B	Unrestricted	1	1

Notice the 3 "TW01" Harnesses. TW01 is the towing electrical connector in the latest schematic for the SOP16 cars. "C" Revision appears to be for HW3 cars. "D" may be for HW4. And then a single harness for the Plaid without a tie breaker.

My guess (and it's a wild one) is that the -01-C is the Rev1 Tow "Two Connector" harness. The -71-C may be the Rev2 Tow "Single Connector" harness.

I think the D Revision harness might only support the Rev2, "Single Connector", J-K part number tow bar. Hence the single TW01 harness.

I'm not sure if the Plaid cars might just have a connector in the 01-B Rev harness.

The Rev1 vs Rev2 is outlined in the Toolbox 3 programming instructions for the tow bar retrofit in the Service Manual.

 

[drop]

Alright folks, I've successully installed the Tekonsha 119147 unit in my Plaid.

I used the guidance provided from this post:


But bearing in mind 2 things:

1. The "brown" wire on the passenger side turn/brake signal is more like VERY light brown, more like salmon/pink colored

2. Tekonsha probably wants you to have this unit installed on the driver side, because the green wire that comes out of it for the right turn signal is much longer than the yellow wire for the driver side turn signal, but given that the power and ground taps I used are on the passenger side and I didn't want to extend those wires and keep the Tekonsha unit in the passenger well, I swapped the yellow and green wires

For those interested, I made a short video showing and explaining the way I installed it:

I wanted to jump in here to confirm that this also works on the 2022 Model S, with the newer tail lights. The only difference is you do need to use the red wire for brakes, because the new tail lights have separate lights for the turn signals. Here's the color configuration for the new tail lights:
Right turn - Light Brown
Left Turn - Green
Brakes - Purple
Tail lights/running lights - White
One note about the white tail lights wire. I didn't want to tap into it directly behind the connection to the tail light, so I followed it up towards the front of the car and made the connection a few inches away from the amp. At that point, there's another white wire the same size that is for the passenger side trunk light. The tail light wire is ever so slightly greyer than that one. I had to take a picture and zoom in to tell the difference.
Also, my Tekonsha unit did not come with the fuse holder - only the fuse. I happened to have one from another unit, so I got lucky. I don't know if that was an error on Tekonsha's part, or if that's just how they come, but I did notice that Amazon suggested a wiring kit that comes with a fuse holder, so maybe that's just how it's normally done. So you might need an Inline Fuse Holder Harness for a 15 amp fuse.

Has anyone figured out what that red wire that we used for power is actually powering? I imagine it's sending power to the amplifier, or a speaker or something. I'd like to know in case I hear a strange noise or have a problem with something.