Arduino Webasto Shower Project

The purpose of this project was to take a Webasto coolant preheater and replace its ECU with something that can (a) control the unit and (b) run it as a shower.

There are plenty of coolant heaters out there that run purely off 12V and don’t require Can-Bus or K-Line signals to turn on. The heater we are using does, so it’s ECU has to be replaced with a custom board.

Firstly I’d like to give credit to the original design for this –
This was the inspiration for this project. I’d also like to that Andrew who made the board and wrote/fixed 99% of the code.

Design and components

Ok, here we go.

The main heater is circled in blue. This is a Webasto Thermotop V. Found in Land Rovers, Jaguars etc as an engine coolant preheater. It is diesel fueled and outputs approximately 5KW.

To feed it fuel we use a 22ml diesel pump. It’s the most common size used on the Chinese diesel heaters.

For pumping the water for a shower it is just a 12V coolant pump.

Front of board
Rear of board

This is the board you are going to build. It’s also the first board I’ve ever soldered components onto from scratch. So if I can do it, you can do it.

Rather than try to explain where each component goes and why, I hope the pictures are enough to make sense of it.

Parts List

1 x Arduino Pro Mini ATMEGA328P 5V 16MHz
1 x 5V Voltage regulator
1 x 100K Thermistor (exhaust temperature)
1 x 1K ohm resistor
1 x 5K ohm resistor
1 x 100K ohm resistor
1 x Momentary switch
1 x Heatsink (for the MOSFETs)
4 x 100 ohm resistors
4 x 4.7K ohm resistor
4 x Diodes
4 x International Rectifier IRLB8721PBF
5 x Phoenix Contact, MSTBA 2.5/ 2-G-5.08, 2 Way, 1 Row, Right Angle PCB Header
5 x Phoenix Contact, MSTB 2.5/2-5.08 PCB Terminal Block
Arduino header pins (male & female) unless you got them with the Arduino

Webasto ThermoTop V
12V coolant pump
22ml diesel pump
Soldering iron + solder etc

The Code & Board

The working code is stored on the BitBucket server here –

You’ll need all the files.

Low_smoke.ino is the main file to open in the Arduino software

Webasto.brd is the board design file.