M21 heater clicking

[rrob311]

I just got my m21 heater going. It seems to work OK however when the temperature stabilizes I hear a loud click in between switching speeds. Is this normal? What is the loud click? It also has some higher yellow flames in the chamber when it is on high. It hasn't shut down yet but I am concerned with the yellow flame. When it is on low is has a steady blue flame.

[hawkins111]

The noise you hear is the solenoid damper. It closes for the low part of the burn and then opens for the high part. If you have a high yellow flame on high you need to put and new mat and ring in your burner.