Installing the Auxiliary Power Relay Board

These steps are generalized instructions.  Any changes you make to your car are your responsibility.  Be sure you understand the entire process and make sure you follow any safety precautions required.

The auxiliary power relay board is designed to use a secondary higher current power source to power the steering wheel while still maintaining compatibility with car firmware updates.

The auxiliary power relay board should be installed near VCLeft (which is found in the drivers footwell on the left side).

You should end up with something resembling the following picture once you have finished the install

 You can see the relay board at the end of the purple and red wires in the middle of the image.

The Auxiliary Power Relay Board has 4 wires that come out of it.  2 purple, 1 red, and 1 black.

The 2 purple wires are for connecting to the original OEM location for steering wheel power, and connecting to the wire that leads to the steering wheel.  The red wire is for connecting to an auxiliary power source, and the black wire is for a ground connection.

To access VCLeft the side trim needs to be removed.  There is documentation available on Tesla's service site.  There are also some youtube videos that can help with the process (a good one that has an overview of the process can be found here).

Once you have access to VCLeft you can start to install the auxiliary power relay board.

Ensure that you have powered down the car completely.  There are a number of guides and videos available to do this.  Follow them!

You will be removing connectors that control parts of the car.  You MUST make sure that the car is in a safe, powered down state before you do that.  Follow the instructions and be safe.

There are 2 purple wires that come with crimped on ends to match the required connections that already exist in the car.  To attach these wires you will have to remove the existing connector and then remove the current wire/pin from that connector.

The connector on VCLeft that needs to be removed is visible as the connector at the top right once the trim pieces have been removed.

A closer view

To remove the connector lift up on the black locking arm (there is a small safety catch in the middle of the arm that you need to depress to disengage it and allow the arm to move freely).

The locking arm will start to push the connector free from VCLeft, but you may have to pull it the last little bit once it has reached its limit.

With the connector removed from VCLeft you can now start on the process of removing the required pin/wire from it.

The wire in question is a purple wire at the "back top" of the connector.  

To successfully remove this wire/pin you need to disengage the locking bar on the larger connector.

The bar does not completely remove from the connector.  You only have to get it open as far as you can see in the above image.

Once you have disengaged the locking bar, the pin can then be pushed/pulled out of the connector.

A pin removal tool such as the one seen in the following image can be helpful in pushing the pin out.

Using a tool like that (or something equivalent) you can push into the slot above the pin and help in coaxing the pin/wire out

Once the pin has been removed you then need to find the matching female pin that is connected to the auxiliary power relay board.

This pin can then be inserted into the larger connector in the same location.

Then find the male connector attached to the auxiliary power relay board and plug it into the original female connector you just removed from the connector (be sure to have some heatshrink tubing or tape on hand to cover up the connection after).

You can then re-connect the connector back to VCLeft and push the locking lever back down till it is secure.

Next up is the ground connection.  There are a number of places you can get a ground from.  Typically any chassis connection works.  One place that is close by and not to hard to get to is directly below VCLeft.  You have to pull some carpet out of the way a little, but once you do access with a socket and extension isn't that bad.

 

In both of the above images the existing bolt has already been removed.  Be sure you don't drop it down into the car when removing it.

You can then prepare the ground wire (black wire) with the provided ring terminal.  You need to crimp it securely and then heat up the plastic to shrink it (and melt the glue to ensure its a good connection).

Once done you can then place it on the existing bolt you removed and screw the bolt back into the same hole.

This is a little easier because now you can use the wire you just attached to keep the bolt in the socket.

With the ground now installed you can take some time to organize the wires and auxiliary power relay board and get everything mounted up.

Some zipties help wrangle the wires and keep everything nice and secure.

At this point you can place some tape over the final red wire and drive around in exactly the same state as you were before you did all this work.  The car will operate just as before.

To finalize the install though and get a higher current feed to the steering wheel you will need to connect the red wire.  There are a number of places that it can be connected.  This documentation will outline one of the options, but if you are interested in others you can join the support discord (link here) for more information.

Any higher current feed should be completed using 14 gauge wire.

One higher current feed can be sourced from the PCS.  This is accessible under the rear seat.  To get to this you need to run a wire up under the trim on the drivers side of the car.

Under the B Pillar trim and then up under the trip leading to the rear seat

You can then run the wire across the back seat and secure it to existing wire bundles to get over to the right side of the car and the PCS 12v lug.

Cut the fuse block loop provides so that you have a longer tail and a shorter tail.

Feed the longer tail through the side of the protective cover and crimp and heatshrink on the ring terminal.  Then remove the bolt and attach the ring terminal and then place the bolt on top.

The shorter tail can then be sliced into the wire that was run from the front of the car.  Ensure that it is affixed security and protected.

The wire can be attached at the front of the car now.  Connect the red wire from the auxiliary power relay board to the wire that runs to the back of the car.  Again ensure that the wires are connected security and protected.

Double check and verify all your wiring.  Ensure that everything is protected, secure, and safe.

You should use a 7.5A fuse in the fuse holder to protect the auxiliary power relay board.

Once all wiring has been completed you can power the car back up and verify that steering wheel heat works.