Tesla stopped supplying 12V power to the aux pin of the 7 way - Fixed!!!

[gglockner]

For the record, I got a Curt 58270 and confirmed that the 2022 Model X also does come from the factory with 12V power on the 7-way connector. I believe I could follow the great instructions from @ShawnA but to be extra safe, I’ll just let Tesla fix this during an upcoming service appointment.

 

[gglockner]

Grrr:

Concern: customer states no 12v power to trailer brake controller
Technician verified the client concern while the vehicle was in for service. Diagnosis determined that the trailer controller is operating properly at this time. Tesla supplies the trailer with light control but not brake controls. Brake lights will work on the trailer but it will not control application of the brakes on a trailer. The vehicle is equipped with a connector and harness for the third-party controller if it is wished to be installed onto the vehicle. No repair needed at this time, vehicle is operating properly with no faults present.

Looks like I have to figure out myself how to supply the constant 12V to the 7-way controller.

 

[ShawnA]

Hi @gglockner ,

I would make a recommendation.
Please do not roast the recommender...

Purchase a hard wired trailer brake controller..
I like Prodigy P3 - Roughly $150

I think you said you had or were ordering the 4 wire
trailer brake harness for Tesla - Sorry I do not have the part number...

Instructions for installing the 4 wire harness:
One wire is common - Negative
Second wire is 20 Amp Positive
Third wire takes signal FROM Tesla brake light
Fourth wire supplies Pin 4 Brake Controller output in 7 Pin.
Wire per these instructions and you will have functioning trailer brakes...
Without the above steps Pin 4 in the 7 Pin does NOTHING.
When you touch the brakes - the controller takes the brake light input
(modified by your setting of the inertial switch.) and supplies
a variable amount of voltage and current to pin 4 of 7.

At this time...
You will NOT have a Hot or Positive Pin 2 in the 7 pin harness.
I have simple instructions for making Pin 2 "Hot."
Disconnect the 7 pin receptacle from the car which will entail
Disconnecting a large Molex connector...

There are positions for 4 heavy gauge wires in the corners of the
connectors - 3 corners from the car have wires populated and the
4 th is empty and plugged.
When you match the plug from the car and the plug to the 7 pin
you will see 2 of the wires mate with each other. The third wire
is at the diagonal corner from the other wire - They do NOT match
hence no power to pin 2.
We found that the easiest way to make pin 2 hot was to move the wire
in the plug to the 7 way to the diagonal corner.
Now the wires mate and there is power to pin 2...

Please look at the connector below to visualize the work...



The tiny pins in the central rows are for lights - brake, turn, and reverse.
The heavy conductors are on the corners for Positive, Negative, and Brakes.

Good luck,

Shawn

 

[gglockner]

Hi @gglockner ,

I would make a recommendation.
Please do not roast the recommender...

Purchase a hard wired trailer brake controller..
I like Prodigy P3 - Roughly $150

I think you said you had or were ordering the 4 wire
trailer brake harness for Tesla - Sorry I do not have the part number...

Instructions for installing the 4 wire harness:
One wire is common - Negative
Second wire is 20 Amp Positive
Third wire takes signal FROM Tesla brake light
Fourth wire supplies Pin 4 Brake Controller output in 7 Pin.
Wire per these instructions and you will have functioning trailer brakes...
Without the above steps Pin 4 in the 7 Pin does NOTHING.
When you touch the brakes - the controller takes the brake light input
(modified by your setting of the inertial switch.) and supplies
a variable amount of voltage and current to pin 4 of 7.

At this time...
You will NOT have a Hot or Positive Pin 2 in the 7 pin harness.
I have simple instructions for making Pin 2 "Hot."
Disconnect the 7 pin receptacle from the car which will entail
Disconnecting a large Molex connector...

There are positions for 4 heavy gauge wires in the corners of the
connectors - 3 corners from the car have wires populated and the
4 th is empty and plugged.
When you match the plug from the car and the plug to the 7 pin
you will see 2 of the wires mate with each other. The third wire
is at the diagonal corner from the other wire - They do NOT match
hence no power to pin 2.
We found that the easiest way to make pin 2 hot was to move the wire
in the plug to the 7 way to the diagonal corner.
Now the wires mate and there is power to pin 2...

Please look at the connector below to visualize the work...

View attachment 790798

The tiny pins in the central rows are for lights - brake, turn, and reverse.
The heavy conductors are on the corners for Positive, Negative, and Brakes.

Good luck,

Shawn

First, I appreciate the suggestions. Trailer towing is new to me, and I appreciate your advice. You seem to have investigated this issue thoroughly.

If I understand, you’re saying two things:

1. Best option is a hard-wired brake controller, connected via the 4-pin pigtail inside the vehicle. This is what Tesla recommends in the Owner’s Manual.
2. If you insist on making a 12V connection on the 7-pin brake controller, you have to modify the molex connector as you describe here and earlier. This may work but it is unsupported by Tesla.

It seems like option 1 is the best. That is what I now plan to do.

 

[gglockner]

For the record, I got a Curt 58270 and confirmed that the 2022 Model X also does come from the factory with 12V power on the 7-way connector. I believe I could follow the great instructions from @ShawnA but to be extra safe, I’ll just let Tesla fix this during an upcoming service appointment.

Whoops, giant typo: the 2022 Model X comes with NO 12V power on the 7-way connector.

 

[ShawnA]

Hi @gglockner ,

I saw the typo no way to correct it...

Back to the subject at hand good choice taking Option 1 - It is the Tesla supported way to go.

Comment on Option 2 - You need it to charge a "breakaway" battery or to power
low wattage lights in a utility trailer.
On the Refresh X - The low voltage lithium battery is now 16 Volts.
We may need resistors to reduce the voltage.

Why Option 2 is a bad choice for using with an Echo Bluetooth Brake Controller.
12 Volt power from the brake controller is capable of 20 Amps on Pin 4.
12 Volt power from the car on pin 2 is capable of 15 to 20 Amps (<Subject to correction)
With the Echo controller pulling 20 Amps from pin 2 and the battery charging or
utility lamps pulling 15 to 20 Amps from the same pin it would be 35 to 40 Amps.
An overload and fuse blowing situation all on the single conductor supplying Pin 2...

Good luck,

Shawn

 

[MX LR MSM]

Hi all,
I plan to install the Prodigy P3 Brake controller on my refresh Model X but i can't find the 4 pin pigtail connecting under the dash !
I found only the part for model X sept 2015 to feb 2021 in the parts Catalog # 1072586-00-A (ASY-HARN, TRAILER BRAKE ECU ADAPTER)
Where did you find the 4 pin pigtail harness for refresh model X beginning march 2021 ??
Thanks

 

[ShawnA]

Hi @MX LR MSM ,

I have the 2018 Model X, so I'm not sure about the 2021...
The picture is not the best because it's a dark area.
In mine the connector was very tightly taped to another wiring
harness straight to the left of the light near your left knee.
It is a very cramped area to work in.

There are very detailed instructions in another thread for
installing the Prodigy P2. The installs are very similar.

Installing a Tekonsha Prodigy P2 Brake Controller in a Model X

I've installed a Tekonsha Prodigy P2 brake controller in my Model X. Takes about 45 minutes to do (the second time you do it). I've a 12 page "how to" complete with pictures and part numbers, but I don't want to publicly release it until someone else has installed one using my instructions...

teslamotorsclub.com

Good luck,

Shawn

 

[MX LR MSM]

Hi @MX LR MSM ,

I have the 2018 Model X, so I'm not sure about the 2021...
The picture is not the best because it's a dark area.
In mine the connector was very tightly taped to another wiring
harness straight to the left of the light near your left knee.
It is a very cramped area to work in.

There are very detailed instructions in another thread for
installing the Prodigy P2. The installs are very similar.

Installing a Tekonsha Prodigy P2 Brake Controller in a Model X

I've installed a Tekonsha Prodigy P2 brake controller in my Model X. Takes about 45 minutes to do (the second time you do it). I've a 12 page "how to" complete with pictures and part numbers, but I don't want to publicly release it until someone else has installed one using my instructions...

teslamotorsclub.com

View attachment 794128

Good luck,

Shawn

Hi ShawnA,
Thanks but i know where is the connector on the car but i still don't know the part number of other part (wires and plug). The parts Catalog # 1072586-00-A is for model X sept 2015 to feb 2021. What's the part number for refresh X, built after march 2021 until now ?
Thanks

 

[gglockner]

Hi ShawnA,
Thanks but i know where is the connector on the car but i still don't know the part number of other part (wires and plug). The parts Catalog # 1072586-00-A is for model X sept 2015 to feb 2021. What's the part number for refresh X, built after march 2021 until now ?
Thanks

The part is same for both pre- and post-refresh Model X: trailer brake ECU adapter (part 1072586-00-A). See pictures from my 2022 Model X. Sorry for the poor camera focus.

 

[MX LR MSM]

The part is same for both pre- and post-refresh Model X: trailer brake ECU adapter (part 1072586-00-A). See pictures from my 2022 Model X. Sorry for the poor camera focus. View attachment 794477View attachment 794478

So you bought the trailer brake ECU adapter (part 1072586-00-A) ?
Where, at your Tesla SC ?
You installed it ?
Does it work fine ? BTW, which brake controller did you choose, Prodigy ?
Thanks

 

[gglockner]

So you bought the trailer brake ECU adapter (part 1072586-00-A) ?

Yes

Where, at your Tesla SC ?

Yes

You installed it ?

Not yet. I plan to wire it later today.

Does it work fine ?

Don’t know until I install it and take delivery of my trailer in 2-3 weeks.

BTW, which brake controller did you choose, Prodigy ?

Curt Echo Under Dash. I selected this because I can make a clean install without the controller showing and without worrying about the angle of the controller. Downside is that all adjustments must be done via the mobile app.

 

[MX LR MSM]

Yes

Yes

Not yet. I plan to wire it later today.

Don’t know until I install it and take delivery of my trailer in 2-3 weeks.

Curt Echo Under Dash. I selected this because I can make a clean install without the controller showing and without worrying about the angle of the controller. Downside is that all adjustments must be done via the mobile app.

Hi gglockner,
Thanks for your answer !
Would you please give me a follow up once wired ? Do you plan to test it with your LED tester into the 7-pin plug of your Tesla ?
Tel me if you have 12v on the 7-pin plug or if you'll have to switch red/blue wire as described by ShawnA ?
Thanks again !

 

[gglockner]

I'm an idiot: I wired the pigtail wrong. I have to go back and rewire it again. Will explain soon.

 

[gglockner]

Briefly:

Trailer arrived last week, so I've been swamped with numerous "teething issues". I don't have time to explain right now, but I wanted to post that the Curt Echo Under Dash brake controller is dangerously incompatible with my 2022 Model X. It engaged the trailer brakes at unexpected times, even when driving 55 mph on the freeway. On Tuesday I replaced it with a Tekonsha Primus iQ, which works flawlessly.

tl;dr: don't mess around with other brands, use a Tekonsha brake controller.

 

[MX LR MSM]

Briefly:

Trailer arrived last week, so I've been swamped with numerous "teething issues". I don't have time to explain right now, but I wanted to post that the Curt Echo Under Dash brake controller is dangerously incompatible with my 2022 Model X. It engaged the trailer brakes at unexpected times, even when driving 55 mph on the freeway. On Tuesday I replaced it with a Tekonsha Primus iQ, which works flawlessly.

tl;dr: don't mess around with other brands, use a Tekonsha brake controller.

Thanks for the hint ! Have a nice ride with your MX / Bowlus !

 

[Clintos]

I'm coming back to the OP's original message that the aux pins on ~2018+ don't provide power. I can confirm the problem on the 2020 LR+.

I referenced this post in my request for the Tesla SC to fix the pin. Service said that the depopulation of the power was intentional to protect the 12v system and would not fix it. It's nearly comical since the owners manual says any problems related to towing are not covered under warranty anyway.

If you're willing to undertake the change to the molex connector yourself, it will add 12v to the aux pin; but Tesla seemingly wont help anymore.

The Tekonsha P2 Prodigy continues to work just fine when wired.

 

[gglockner]

The Tekonsha P2 Prodigy continues to work just fine when wired.

This is the way.

 

[Clintos]

This is the way.

Airstream of Utah first had me try a wireless model. It appeared to have zero compatibility with my X.

 

[gglockner]

Airstream of Utah first had me try a wireless model. It appeared to have zero compatibility with my X.

That was my experience with a Curt Echo Mobile. As best as I can tell, Tekonsha is the gold standard, and several of us have good experience with their wired brake controllers in the Model X. For me, the Primus iQ is all I need.