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 – https://maelpoureau.com/webasto_shower/
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.
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.
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 – https://bitbucket.org/davidmcluckie/arduino-shower/src/master/low_smoke/
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.