I had to poke at the unit, try to read the garbled numbers and wait for the air to start blowing somewhere without knowing whether it was supposed to be hot or cold. It was like playing with dyslexic el ni o.
Fortunately I found a cheap solution. Module Master makes a $53 LCD rebuild kit:
Module Master Porsche Climate Control LCD Rebuild Kit
It includes instructions and is very easy to install.
For some pictures from my install, check the link below.How the display looked originally:
The unit out of the car:
The rebuild kit: