Enter debug mode: 1. Remove a battery. Press and hold the MODE button, then insert the battery. The screen is shown in Figure 1. 2. Short press the right button to enter the debugging mode. The screen is shown in Figure 2. Note! Determine the temperature in the room. The current indoor temperature is 26°C, So we adjusted it to 26°C. Short press the left button or the right button to increase the temperature and decrease the temperature until it is the same as the indoor temperature. 3. Pull the trigger. Ready to use. What function do you want to debug?We can try to debug it for you! We will solve it for you asap! Wish you a happy life! There will be a deal today: 25% off! April 28 10:35 AM〜10：35PM on Amazon.de https://www.amazon.de/MESTEK-Temperaturmessger%C3%A4t-Ber%C3%BChrungslos-Alarmfunktion-Einstellbarer/dp/B07NY5RH9X/ref=sr_1_40?__mk_de_DE=%C3%85M%C3%85%C5%BD%C3%95%C3%91&dchild=1&keywords=Infrarot+Thermometer&qid=1619597263&sr=8-40