The following cases could be a cause of the above problem.
If any of the above is not your case, contact the shop you purchased the product from or the local HAKKO sales representative/distributor for repair.
If you measure the temperature incorrectly, you cannot obtain the correct temperature value, and sometimes you have a lower temperature than the actual one.
Measure the temperature with the correct method.
Remove solder stuck on the tip before measurement.
Apply new solder to the tip.
Place the tip on the measuring point and feed solder on the tip.
Please do not press the tip end to the sensor too much not to break it.
Please do not move the tip until the display shows a stable temperature.
Measure the temperature in a place where there is no airflow from the air conditioner or the like.
Read the value displayed. (It shows 376ºC in the photo.)
Repeat the above procedure (1 to 4) to find the highest temperature.
If the sensor has deteriorated due to corrosion by solder, the measured temperature could be lower in some cases.
If batteries are low on power, the display may show errors.
Replace it with a new battery before measuring the temperature again.
When the battery is low on power, the 'B' mark circled in red in the photo lights up. If the battery becomes further lower with continuous use, the icon begins to fade and disappears finally.
When the battery is low on power, the battery icon circled in red in the photo flashes. If the battery becomes further lower, the icon becomes steadily lit. In some cases, the screen may display "Low Battery" when you power it on, and then it immediately turns off.
When the battery is low on power, the 'B' mark circled in red in the photo lights up.
If the battery becomes further lower with continuous use, the icon begins to fade and disappears finally.
It happens that you would obtain lower measured temperatures due to oxidation of the tip, enclosure pipe, and nut.
Replace them with new ones.
The length and weight vary depending on the tip shape. If the tip shape is changed, it may cause the temperature to become lower or higher in some cases as the themal capacity is changed.
Make fine temperature adjustment (changing the offset value or CAL adjustment) with the tip you use.
Calculate the offset value from the difference between 'Tip temperature' and 'Set temperature' and the current offset value, and input it to the station.
If the tip temperature is lower than the set temperature, input a positive offset value to the station. If the tip temperature is higher than the set temperature, input a negative offset value.
Adjust the CAL knob using a tool like a screwdriver.
If there is any problem other than above mentioned or you cannot fix, please contact the store of purchase or the Hakko official distributor for solution.