Integrating Non-Wi-Fi Mitsubishi Air Conditioners into Home Assistant via ESP32

Home automation enthusiasts can now integrate Mitsubishi air conditioning units that lack native Wi-Fi into Home Assistant systems for less than 10 euros. By utilizing an ESP32 microcontroller to communicate with the unit's CN105 service port, users can achieve full bidirectional control—including mode, fan speed, and setpoint—without routing data through external cloud servers.

Limitations of Standard Integration Methods

Many Mitsubishi ducted AC units, such as the SEZ-M60DA2, lack official wall thermostats with Wi-Fi, forcing users to rely on physical buttons. Common workarounds like IR receivers are often insufficient for remote access, while using a simple relay to cut mains power can damage inverter units by defeating their ability to modulate power.

The article discusses integrating non-Wi-Fi Mitsubishi units into Home Assistant systems.

Official cloud adapters, such as MelCloud, can cost up to 200 dollars and require data to be sent to private servers. These 'Cloud Polling' methods also require persistent accounts, creating a dependency on the manufacturer's infrastructure and data policies.

Chart drawn by HN Digest from figures reported by radiohackers.com; values are shown as written in the source.

“Totally local solution. My data does not go to private servers.”

— How I Added a Non-Wi-Fi Mitsubishi AC to Home Assistant

The ESP32 and CN105 Port Mechanism

The proposed solution involves connecting an ESP32 board to the unit's CN105 port, which is the same service port used by the manufacturer's own Wi-Fi adapters. By using ESPHome firmware—specifically components inspired by the SwiCago library—the ESP32 acts as a bridge between the AC unit and a Home Assistant instance.

The solution utilizes a reverse-engineered Mitsubishi protocol via an ESP32 board.

The hardware setup requires a JST PA 2.0 mm 5-pin pigtail cable. The ESP32 connects to the unit's TX/RX lines (Pins 4 and 5) and draws power from the 5V line (Pin 3). A specific wiring configuration is required to ensure the ESP32 is not damaged by the 12V line (Pin 1).

The ESP32 board runs ESPHome firmware to act as a bridge for the AC unit.

Local Control and Advanced Telemetry

Because the ESP32 communicates directly with the unit's internal protocol, it provides a bidirectional link. If a user changes a setting via a mobile phone, the physical wall thermostat updates simultaneously, and vice versa. This ensures the system remains synchronized regardless of the input method.

Beyond basic on/off commands, this integration exposes several high-value sensors. Users can monitor the unit's reported room temperature, the outdoor air temperature (reported only while the unit is running), and the actual energy consumption in kilowatt-hours (kWh). This level of telemetry is often unavailable through standard remote controls.

Installation Constraints and Precision

The installation requires physical access to the AC unit's internal wiring to locate and connect the CN105 port, which may be hidden behind tape or panels. Additionally, the ESP32 must be mounted outside of the metal control box to avoid acting as a Faraday cage, which would block the Wi-Fi signal.

While the integration provides robust control, some users note that these inverter units may have basic control laws. For example, some units may wait for a 1 degree Celsius deviation before cycling, which might limit the precision of temperature maintenance compared to high-end PID-controlled systems.