Furnace question

[Charlie1022]

The other day I was walking around the motorhome and noticed what appeared to be some type of fire brick in the furnace exhaust port on the outside of the coach. I reached in with my finger to see what it was and it was very soft and turned to powder. Has anyone else ever found anything like this and what was the cause?

[FatChance]

Mud dauber bee nest?

[Trans. Cajun]

I would guess you had a mud dopper nest. That is a mud nest made by a wasp type insect.

[Charlie1022]

This was not a mud dopper nest. The material was like a soft chalk and had a red tint on one edge.

[Gary RVRoamer]

There isn't any "firebrick" in either an Atwood or Suburban furnace, so it's something else. Maybe a foreign object or some piece of coach wall insulation that has fallen down. There is a divider gasket between the exhaust and the air inlet that is critical to operation, so make sure that hasn't fallen out of place somehow. It prevents the air intake side from sucking exhaust gas directly into the intake.

[Charlie1022]

Checked it out further and it really was a mud dopper nest.