Here are some hints and clues concerning the HVAC system of the Roadster and the given values in service menu:
after a long journey and a SC which wanted to sell me a DC/DC System for 800 Euro (even a bit more) to deal with my concerns I found out the following:
if the HVAC system contains no or in my case only a left over of 50g of liquid coolant the service menu will show a value of 31.8 Bar (which is ridiculous high) - I exchanged the measurement sensor and still given the same value (only connected a replacement sensor, not connected to the high pressure pipe)
I exchanged the DC/DC converter in the front (responsible for the HVAC and heating system of the cabin, HVAC is also used over a heat exchanger for cooling down the coolant of the battery) - thats why the front fans and HVAC compressor sometimes kick in while charging or giving the battery a hard time burning some rubber
I went to a garage which allowed me to use their equipment for HVAC maintenance. Most garages make a denial when you mention the 400 Volt
While sucking the 50g leftover coolant out of the pipes the measurement of the HVAC went from the default value 31.8 Bar to 0.
Ater a 20 minute vacuum of the HVAC (leckage check) and no air coming into it I was able to refill the system with 750g of refigerant coolant.
Value went from 0 to 3.0 Bar.
Immediately after the filling was done and the HVAC was started the compressor would start to run and pressure would go up to 19.8 Bar.
Since then (a few days now) HVAC is working fine and when cooling of battery fluid is requested the HVAC woould start to run,
Conclusion and remarks:
My SC wasnt able to determine that there was almost no coolant refigerant fluid in my HVAC system anymore (guys that's a no go and I will have a talk about that in the SC in the next weeks for sure!) THIS IS PART of the maintenance plan!!!
They wanted to exchange the DC/DC converter in the front (which is often a cause for problems due to moisture problems - I have to admit) for quite a few bugs (btw. I counterchecked with a used one... and got the same values and behaviour of the car)
nowhere is mentioned that the pressure sensor of the HVAC will show value 31.8 Bar when theres (almost) nothing in the HVAC anymore.
SC didn't know that front fans have to kick in after starting HVAC for cabin in a few second (also when cooling is requested by the system for the battery)
Raodster is holding pressure at about 4.8 Bar since I filled it up... and the best: filling up cost me 80 bugs and a few bugs for the mechanic who helped me...
BTW: you might check the website of Eberspächer in Germany and be astonished how many standard parts of them are used in the Roadster
It seems i have same problem. Got car 2 weeks ago. Is there service manual still available? Dropbox link does not work...