Simply start the Autoterm Air parking heater via app

The parking heaters from Autoterm, such as the "Air 2D" model, have established themselves in the motorhome community as a reliable and efficient heating solution. While the supplied control panel fulfills its purpose, many users would like a more convenient solution: being able to start the heating remotely - for example, when you come back from a hike or the ski slope and want to preheat.

In this article, I'll show you various ways to control your Autoterm heating remotely, from the official solution to a smart DIY hack.

These options are available

Bad, but simple: The official GSM module from Autoterm

With its GSM module, Autoterm offers an official solution for remote control. The module is connected between the heater and the control panel and enables control via smartphone app.

However, the disadvantages clearly outweigh the advantages:

• A separate SIM card with data volume is required
• Communication takes place via SMS commands - even if you use the Autoterm app
• With a price of over €100, the module is relatively expensive

A look at the official Autoterm app in the App Store confirms the outdated state of the technology: last updated in 2019, poor ratings and a user interface that has long since seen its best days. In the age of IoT and smart homes, this solution is simply no longer up to date. The dependence on a functioning mobile phone connection at the parking space and the ongoing costs for the SIM card make the system unattractive.

Smart, but complex: Proxy module between heating and control panel

For the technically savvy, there is an elegant solution: a self-built proxy module that is connected between the heating and the control panel. This solution enables complete control over all heating functions.

The principle:

• A microcontroller (usually ESP32) is looped into the serial communication between the heater and the control panel
• The controller "eavesdrops" on the communication and can feed in its own commands
• Integration into Home Assistant or other smart home systems possible

The challenges:

• The serial protocol must be reverse-engineered
• Knowledge of electronics and programming experience are essential
• In the worst case, errors can damage the heating system
• The time required for development and testing is considerable

Projects like Robert Schröder's show that it works, but for most users the effort involved is disproportionate to the benefit.
I have already experimented with this solution and have also developed and produced a prototype for my own communication board, which uses an ESP32 and can be plugged between the control unit and the heater. However, the software is not yet fully developed. As soon as I am ready, there will be a separate article on this blog.

Good compromise: Use of the existing emergency start cable

The most elegant solution uses an existing function of the Autoterm heaters: The emergency start cable. This function is already integrated in every Autoterm Air 2D and is just waiting to be made smart.

This is how the emergency start works: There is a brown and a white cable on the wiring harness of the heater. If these two cables are connected to each other, the heater starts immediately at the highest level and runs for exactly 2 hours. This function is actually intended for emergencies when the control panel fails. Tigerexped has written a more detailed description of where to find the cable.

As soon as the two cables are connected together:

• When connecting, the heating starts at maximum power
• The heating switches off automatically after 2 hours
• Reconnecting starts the cycle from the beginning
• Disconnecting the cable stops the heating

This function can be used perfectly for remote control without having to intervene in the complex electronics of the heating system.

But how do you use this emergency start cable?

The hardware: Shelly 1 Mini as a smart switch

The Shelly 1 Mini is a miniature WLAN-capable relay that is perfect for this task. With its compact dimensions and a price of just €15-20, it is the ideal solution for our project.

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Alternative: Shelly 1 If you want to invest a little more, you can opt for the Shelly 1. This slightly more expensive model (approx. €25-30) offers a decisive advantage: a temperature sensor, such as a DS18B20, can be connected via the AddOn module. This means you can not only start the heating, but also directly measure the temperature in the interior and check how warm it has already become. This is particularly useful for checking whether the heating is actually running and whether the interior has reached the desired temperature.

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The wiring: The brown and white cables of the heater are connected to the switch output of the Shelly, the Shelly itself is supplied with 12V from the vehicle electrical system. There are many instructions on the internet for the exact wiring and connection details on how to switch a switch with a Shelly.

Additional control option: A switch or button can also be connected to each Shelly. If you want to install a physical button in the motorhome in addition to the Wi-Fi control, this is no problem. This way, you always have a backup solution in case the WiFi doesn't work.

The software configuration

How to set up the Shelly: The Shelly can be set up using the free Shelly app. After the first start, the device creates its own Wi-Fi hotspot to which you connect. You then enter your camper WiFi access data in the app and the Shelly is online.

The correct operating mode: It is important that you operate the Shelly in "Momentary Switch" mode. This means that the relay only switches for a brief moment (approx. 0.5 seconds), simulating a button press. This prevents the cables from remaining permanently connected.

Integration in Home Assistant

The integration into Home Assistant is particularly interesting for smart home enthusiasts. Shelly devices are officially supported by Home Assistant and can be integrated with just a few clicks. Once integrated, you can not only control the heating manually, but also create complex automations.

Requirement: WLAN in the motorhome

This solution assumes that a Wi-Fi router or mobile hotspot is available in your motorhome. This may seem like a restriction at first glance, but in practice it is usually not a problem. Most modern motorhomes are equipped with an LTE router anyway, and many campers already use mobile hotspots for internet on the road.

If you don't yet have Wi-Fi in your camper, buying a mobile router is doubly worthwhile: not only do you have Internet for your devices, but you can also control your heating smartly. Inexpensive LTE routers are available from as little as €50, and with a data card you are independent of the often slow campsite Wi-Fi.

I have had good experiences with Teltonika products. Compared to cheaper routers from Huawei, for example, you can insert 2 SIM cards and switch between the SIM cards automatically, e.g. when reception is poor. Here an older and a newer model with 5G from Teltonika in comparison with a mobile LTE modem:

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Alternative: Control via the Shelly Cloud

If you don't use a Home Assistant, you can also control the heating directly via the Shelly app. The Shelly Cloud offers a number of practical advantages:

• Access from anywhere in the world
• No need for your own server infrastructure
• Simple timers and scenes
• Push notifications for status changes
• Free of charge and without subscription fees

Conclusion

Using the emergency start cable in combination with a Shelly 1 Mini is the perfect compromise between functionality, cost and complexity. With a budget of less than €20, you get reliable remote control of your Autoterm heating that can be seamlessly integrated into existing smart home systems or the Shelly app.

In contrast to the overpriced GSM solution, you don't need an additional mobile connection, and compared to the complex proxy module, installation is completed in less than an hour.

The only restriction - the heating always runs at full load for 2 hours - is usually not a problem in practice. Anyone who starts their heating remotely usually wants a quickly warm motorhome anyway.

After two winters with this solution, I can say that there is hardly anything better than getting into a pre-warmed motorhome after a cold day on the slopes. The investment has already paid off after the first use.