Activate Webasto diesel heater using OMS and Azure functions

Looking at the above picture snow and winter is pretty awesome, but when you have to fire up your car outside your cabin in -15c (5f) you wish for summer. Not only is it extremely hard for your engine, but it’s also ridiculously cold to get inside the car! That’s why many cars in Norway are equipped with preheaters. A unit you can activate before starting or entering the car, heating up the engine (and in many cases the interior as well).
Just to put some numbers down, average temperature in Oslo January 2017 was -4.3, and coldest -12.6.

My child carrier, a Range Rover Sport, (one of Britains fines engineering that never fails) is equipped with a Webasto pre heater and controlled remotely by SMS command or an app. Communication is using WBUS, Webasto’s own language.

My goal in this post is to use data from the OMS Weather Data solution and Azure functions to automatically start my Webasto heater based on the observed temperature. I have to say, using the app directly way easier, but this is a very good opportunity to explore and play with cars, azure and automation.


Starting the heater

Many of these heaters and apps only communicate using SMS commands, but my heater controller can use internet connection as well, meaning there is an API of some sort it’s communicating with.

Using fiddler I found out how the app was communicating, replicating it using Powershell I ended up with this as a simple function to send commands to my heater. Typical commands are “cmd_heater_status” which asks for current status, and “cmd_time1:30,start” that starts the heater for 30 minutes.

To be honest, I wasn’t very pleased with the security here, but that’s something I will notify the company who make these controllers about.

Below is a typical output after requesting heater status.

heater : 1
gsm : 7
voltage : 12.0
h_temp : 25
flame : 0
date : 2017-10-1 19:13:9
valid : 1
status_date : 01/10
status_fdate : 01.10.2017
status_time : 21:13:09

Creating the Azure Function

After we have the basic functionality in place, we can add some logic to our script and create an Azure Function out of it. I have created a basic Powershell function below that accepts two input parameters. TempLow the temperature you have to be below to fire the heater, and heatingMinutes which is the number of minutes the heater will run.

The rest of the script is using our function above to request statuses and act upon our input and the heater response. I had to add sleep time within the script so that the Webasto controller had time process my commands.
Parameters like email-address and heaterId are defined as function environment variables


OMS / Log Analytics setup – query and alert.

Using data from the weather solution I created together with Cameron Fuller i created the following query to alert when observed temperature in Oslo is below a certain degree. This search is based on the new query language, Kusto. I reccommend everyone (including my self) to take a look at this Kusto cheet sheet.

YRno_CL | where LocationName_s == "Oslo" and TimeGenerated > ago(2h) | summarize AggregatedValue = avg(ObservedTemp_d) by bin(TimeGenerated, 15m), LocationName_s

Create an metric based alert based on the above query.

To kick off our Azure Function we set the alert to send a webhook with a custom json payload looking like this: (yes testing values)

"tempLow": "59",
"heatingMinutes": "40"

The test says webhook is sent successfully, and our function log confirms 🙂


Calm down John Snow, let winter come.


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