The other thing is, that I found out that the step up inverters + the micro heating coils are a bit of a weak link – to get a vacuum I need to evaporate hot water – and as long as the system is not under a vacuum I need to heat up a tiny bit of water to produce the vapor, which removes the air. At first I only used a micro heating coil, but at 12 volts it was too powerless. Then I added a step up inverter, but those were of misserable quality. From one of the new 9 EUR parts a coil fell of right away, I had it reasoldered (stupidly the wrong way around) which destroyed it.
The second one had another issue – the coil loosened and so it took me while to found out why it showed 0.2 volts instead of the 20 I needed. Soldered it (this time right way around), worked again.. fell of again. Then the first micro heating coil broke… ARGH. So after these attempts I needed to shift my attention to the oher projects I have, because they were simple more needed at the time (no fun sitting in the car, with the mosquitos coming in when the windows are open). But I will be back at the project, after I solve the most critical problems we had up until now (appart from officials stuff, so purely car related..)