Arduino + LCD + webasto thermo top V

Testing some code I put together to control a Webasto thermotop V heater via its w-bus line.
The code can switch the heater on and off, and displays some information on the LCD display showing the current temperature / voltage / and flame detection.
I also display the glow plug resistance (used for flame detection), and what is supposed to be some indication of power output but it does not seem to be displaying correctly.
It also displays 4 vertical bar graphs relating to the various levels of things like the circulation pump, combustion fan speed, fuel pump speed, and glow plug heating level.
Arduino pins 18+19 give out serial data, which is fed to a L9637D converter chip, which converts the signal to wbus (K-Lline).
Code (bit rough and ready but people asked for it).
pastebin.com/9j...
WBUS.H (borrowed from the pic micro version)
pastebin.com/8e...
Picture of how to wire up the L9637D chip.
www.labkit.ru/u...