Heating system

Can anybody explain the heating system? I can't find anything about first and third slider in the manual nor about the button on the top.
It seems I can't find right setting for cooling... the temperature always goes over 30°C and the passengers complain. I think I tried every combination of sliders but nothing.
Are there simple steps how to cool down your bus and how to warm it up?

>>> Click this <<<

In addition to those heating controls, you might want to cool the bus. To do this, simply ensure you are having no heating on, then open your cab window, the passenger windows and if necessary, the front and back doors. (In order to release the bus with the backdoors open, release the bus stop brake when they are open and turn the master switch on and off.)

Thank you!

I get it now.. you can't cool the bus with this system... I thought that if it's on blue it's cooling the bus and if it's on red it's heating. But that's not the case. It's just a heating system.