“Rattling sound” in ceiling when a/c is running?

[RickandBecky]

We have a 2020 30.5 CKTS with two a/c units (Whisper Quiet). When the unit in the main living area is running, we can hear a noisy rattling sound coming from both of the large return air grills, and also hear it when standing or sitting in between the two grills. I have been on the roof, taken off the shroud from the rear unit—totally quiet when it’s running (hear no unusual noise, and no wasp nests or anything hitting the fan). Also, when that unit is off, and our bedroom unit is running, there is no noise—totally quiet! Not sure what else to do, as I’m sure it’s something loose in the ductwork in the attic between ceiling and roof. Anyone have any thoughts or ideas for us, short of taking to the dealership right now? Thanks very much!

[AKRUEBBE]

Originally Posted by RickandBecky

We have a 2020 30.5 CKTS with two a/c units (Whisper Quiet). When the unit in the main living area is running, we can hear a noisy rattling sound coming from both of the large return air grills, and also hear it when standing or sitting in between the two grills. I have been on the roof, taken off the shroud from the rear unit—totally quiet when it’s running (hear no unusual noise, and no wasp nests or anything hitting the fan). Also, when that unit is off, and our bedroom unit is running, there is no noise—totally quiet! Not sure what else to do, as I’m sure it’s something loose in the ductwork in the attic between ceiling and roof. Anyone have any thoughts or ideas for us, short of taking to the dealership right now? Thanks very much!

Have you removed the grill from the return ducts to see if anything is flapping inside the return?

[Screwby]

We had an AC on the 5th wheel that rattled when it ran. I took the ceiling shroud off and the “squirrel fan” was rubbing ever so slightly against the foam insulation next to it. Would make a chattering/rattle sound ever time it kicked on. I reached up and shoved the insulation over 1/8” and it’s been fine ever since. Maybe you have a similar issue.

[RickandBecky]

Yes, I removed both air return grills and looked inside, as best I could, with a flashlight and saw nothing moving or flapping around. I can’t see how to get to any of the ductwork without taking part of the ceiling down. Not a job I want to tackle unless it’s easier than it looks to be.

[Screwby]

Maybe buy one of those cheap cell phone probe cameras off Amazon so you can look a little deeper? Be a fun toy to have regardless

[RickandBecky]

Our rear a/c doesn’t have a shroud to remove (all on the roof). But there are two air return ducts in the ceiling on either side of the living area ceiling. I’ve pulled both the grills off of them and checked with a flashlight and saw nothing moving, flapping, etc. Checked the fan under the shroud on the roof, and it was clean and quiet running. Puzzled where to look next. Thanks for your reply!

[RickandBecky]

Originally Posted by Screwby

Maybe buy one of those cheap cell phone probe cameras off Amazon so you can look a little deeper? Be a fun toy to have regardless

Thought about doing that! Good idea, thanks!

[RickandBecky]

Originally Posted by Screwby

Maybe buy one of those cheap cell phone probe cameras off Amazon so you can look a little deeper? Be a fun toy to have regardless

Like the idea of a little camera to look a little deeper inside ductwork/ceiling. I’ll look for one online. Thanks!

[North of 49°]

During one of our recent trips, we encountered an overwhelming awful smell as soon as we turned on the A/C. Fearing a dead mouse in the ducts, I removed the interior panel and started looking around. As I did so, a small piece of foam fell out from somewhere; I didn't see where it came from. Didn't find any dead mice either, but I did re-tape all of the ducts where I could reach.

After I closed everything up again, there was a rattle coming from the A/C. I though that the foam piece that fell out was responsible for stopping that. I didn't have the foam anymore, so I found a piece of foam packing material and put it where I thought the rattle was coming from, and that seemed to solve it.

And the bad smell? It never came back again and I never discovered the source. I blame the dog.