Heater popping noise after heating up and shortly after turning off

[steamboatscott]

Took my 2013 Flagstaff 228 on a maiden voyage this weekend and only had one minor annoyance - the heater would make a popping sound (about 3-4 times) shortly after it fired up and shortly before the fan turned off. I removed the cover and couldn't see anything obvious. It sounds kind of like my Mitsubishi ductless air conditioners (in the house), which makes noise as certain elements expand/contract when getting cold (except the heater in my PUP sound is much louder). Any other thoughts as to what to look for?

When I first heard the sound, I thought it was just the igniter firing off, but then it happened at the end of the cycle and repeatedly throughout the night. Dealer of course has offered to look at it, but they're 3 hours away in no direction I ever want to go camping.

[BigBaron]

Sounds like something is expanding inside. Heat shields, heater cover, or?
I'd look around inside. You'll probably see it.

[Herk7769]

Check the flue for obstructions (like a spider or wasp nest).

You can try using compressed air (can or compressor) to see if any junk got in there.

[OldCoot]

I would guess it is a normal expansion and contraction of the heating chamber and other parts. It's probably louder because you're a lot closer to it. Water heaters also sometimes make noise while heating due to residue in the bottom of the tank.

[RalphieAdie]

Mine makes similar noise. Shortly before the fan cycles off. Our's can't be due to wasps, as we took delivery in the cold weather; didn't hear the clunking initially; yet within a few trips the clunking started (heard it in late November for the first time).

It's on our list to have the tech's take a look at during "The International".

[F and E Damp]

Check the tightness of the W/H mounting bolts. If they're slightly loose, the contraction and expansion of the tank, as it cool and heats, might be building up enough force to move the mounting brackets slightly.