Step 1
Turn off the main gas valve connected to the Takagi water heater. Unplug the water heater from the electrical outlet.
Step 2
Turn the screws in the case in a counterclockwise direction and remove the screws from the case, using a screwdriver.
Step 3
Locate the manifold of the water heater. The manifold is the rectangular piece that covers the combustion chamber. Turn the screws in the case in a counterclockwise direction and remove the screws from the manifold. Place the manifold in a safe place.
Step 4
Locate the damper of the water heater. The damper is the thin rectangular piece with multiple holes. It is located behind the manifold. Turn the screws in a counterclockwise direction and remove the screws from the damper. Place the damper in a safe place.
Step 5
Locate the flame sensor. The flame sensor is located in the center of the combustion chamber. Turn the flame sensor in a counterclockwise direction to remove it from the combustion chamber. Pull the flame sensor backwards to remove it.
Step 6
Rub the exterior surface of the flame sensor gently with steel wool to remove the deposit around the sensor.
Step 7
Insert the flame sensor back into the combustion chamber. Repeat Steps 1 to 4 in reverse order to reassemble the water heater.
Check out this related video from Homesteady on Youtube.