When you have COMPACT AIR II you use the push-button code. You start by opening the door. You then press RES when the alarm appears on the display. 

1. Press and hold button 4 for 6 seconds. 

2. Press button 2 for 1 second, without releasing button 4. 

3. Press and hold button 4 for a further 8 seconds until SERVICE MODE appears on the display.

4. Release the button. 

You now have four choices:

N1 – Return to the Main menu

N2 – Installation menu

N3 – Operating info with times and duct/filter calibration

N4 – Manual test and calibration