# Serin Controller installation

> Connect your Serin Controller to the Mitsubishi indoor unit's CN105 port, position the board and cable, and continue smart-home setup.

Source: https://serin-labs.com/controller/install.html
Last updated: 2026-10-27

Use an assembled CN105-to-Grove cable. If you are making your own, check it against the [wiring reference](https://serin-labs.com/wiring.html) before installation.

## 1 Prepare for installation

1. [Confirm model compatibility](https://serin-labs.com/compatibility.html) and that the CN105 port is available.
2. [Install your chosen firmware](https://serin-labs.com/flash.html) over USB before fitting the controller. Disconnect the USB cable afterward.
3. Have a screwdriver ready and read the [installation precautions](https://serin-labs.com/safety.html).

Important

**Check whether CN105 is already occupied.** An existing thermostat's receiver or adapter may use this port, even if the thermostat itself is wireless. The Serin Controller cannot share CN105 with that accessory; CN105 splitters are not supported.

## 2 Connect and position the controller

Warning

**Switch off power at the breaker, not just at the remote.** The control board carries line voltage. Leave power off until the cover is back on. If you are not comfortable working inside the unit, have an HVAC technician make the connection.

![Connect the indoor unit's CN105 port to the Serin Controller's Grove port with the supplied cable. The cable carries power and communication. Disconnect USB before connecting CN105.](https://serin-labs.com/assets/diagrams/controller-cn105-connection.svg)

**Port locations vary by indoor unit.** Identify connectors by their labels.

1. With power off, open the indoor unit's cover and locate the main control board. Find the five-pin connector labeled **CN105**, usually red and sometimes white. Do not substitute CN110.
2. Seat the cable's CN105 connector in the unit and the Grove connector in the controller. Check orientation against the connector and board markings; do not force either connector. See the [wiring reference](https://serin-labs.com/wiring.html#diagram).
3. Position the controller and cable clear of the fan, heat exchanger fins, and condensate tray. Ensure the cover will not pinch the cable.

[![Close-up of the red five-pin socket labeled CN105 on the indoor unit control board](https://serin-labs.com/assets/gallery/800/mitsubishi-cn105-port-control-board.webp.webp)](https://serin-labs.com/assets/mitsubishi-cn105-port-control-board.webp)

**Indoor-unit end:** the labeled CN105 socket. [Enlarge port photo](https://serin-labs.com/assets/mitsubishi-cn105-port-control-board.webp).

[![NanoC6 controller with the Grove connector seated at the rear and the free five-pin CN105 connector at the other end of the orange cable](https://serin-labs.com/assets/content/800/serin_cn105_controller.jpg.cf751b9c14ef.webp)](https://serin-labs.com/assets/serin_cn105_controller.jpg)

**Controller end:** Grove plug seated in a NanoC6. [Enlarge connector photo](https://serin-labs.com/assets/serin_cn105_controller.jpg).

[![Orange CN105 cable routed beside the indoor unit's control-board enclosure](https://serin-labs.com/assets/content/800/media/installation.jpg.d3034c4a45a9.webp)](https://serin-labs.com/assets/media/installation.jpg)

**Cable routing example.** [Enlarge installation photo](https://serin-labs.com/assets/media/installation.jpg).

A sheet-metal air-handler cabinet can weaken Wi-Fi. If reception is poor, see [placement and Wi-Fi troubleshooting](https://serin-labs.com/troubleshooting.html#wifi-drops) and the [cable length options](https://serin-labs.com/cable.html).

## 3 Replace the cover and restore power

Check the connectors and cable clearance, reinstall the cover, then restore power at the breaker. CN105 powers the controller; leave USB disconnected.

On HomeKit-compatible and Matter-compatible firmware, the [status light](https://serin-labs.com/controller/status-lights.html) shows startup and connection state.

ESPHome uses the RGB LED as a controllable light entity, so HomeKit-compatible and Matter-compatible status colors do not apply.

## Continue with your platform

- [Home Assistant / ESPHome setup](https://serin-labs.com/esphome/setup.html)
- [Apple Home / HomeKit setup](https://serin-labs.com/homekit/setup.html)
- [Google Home, Alexa and SmartThings setup](https://serin-labs.com/matter/setup.html)

If Wi-Fi and app pairing are already complete, go straight to your platform guide's control check.