Hopefully, this explains how the Chinese diesel heaters can be tuned to perfection with no tools apart from your fingers. Out of the factory, they're set at a default value that gets them running. All of the ones I've tested have been terrible. If you follow these 'simple' guidelines, it'll run MUCH cleaner and MUCH more economical.
I am not responsible for any damage caused by tuning your heater. You do this at your own risk!

I've done another video which covers the pump install and where you can buy it    • Chinese diesel heater  silent pump, ...  

A basic description of how to tune it with default fan speeds is:

Turn the heater up to full and leave it to settle for a couple of minutes
Reduce the maximum pump speed (0.1hz at a time) until it drops one bar on the display
Increase the maximum pump speed (0.1hz at a time) until it shows all the bars
Increase the maximum pump speed by 0.2hz to make sure it keeps the heat just over the top bar

Turn the heater down to minimum and leave it to settle for a couple of minutes
Reduce the minimum pump speed (0.1hz at a time) until it drops one bar on the display
Increase the minimum pump speed (0.1hz at a time) until it shows all the bars
Increase the minimum pump speed by 0.2hz to make sure it keeps the heat just over the top bar

Repeat the above until it's all stable.