Faulty heater Disassemble the unit：
1. Turn the nut counterclockwise and remove the tip enclosure and the tip.

2. Turn the nut counterclockwise and remove it from the iron.

3. Pull both of the heater and the cord assembly out of the handle. (Toward the iron tip direction)

Measure when the heater is at room temperature.
1. Resistance value of the heater (resistance between the 2 red wires)≈1Ω

2. Resistance value of the sensor (resistance between the 2 blue wires) ≈50Ω

If the resistance value is not normal, replace the heater.
NOTE：Wire colors may differ from actual.

Replace the heater. (9SS-988-HT)
1. Desolder the faulty heater's leads and remove the heater.

2. Replace it with a new one and solder it to PCB properly.

3. Solder the two leads of the heater to the other side of PCB. Bend the leads at a right angle when soldering to avoid short-circuit

After the heater is replaced.
1. Measure the resistance value between pins 2&5 or pins 3&5 or pins 1&5. If it is not open（∞), the heater or sensor may be in contact with the earthed casing. The problem must be solved otherwise it will damage the PCB.

2. Measure the resistance values between all leads to check whether they are normal. Make sure the leads and the earthed spring are well connected.