I've recently experienced a very weird intermittent "flutter" noise occurring in my coach. It sounds just like a water pump cycling on and off occasionally. I have also noticed that it seems to only occur when it is windy outside. I have a 3921GK and I can hear it most clearly from the bed at the wall separating the bedroom from the shower stall. I pulled off the shower valve/black tank anti-siphon inspection cover in the bedroom to see if I could pinpoint the origination. I can hear it but it's definitely not the pipes or anti-siphon valve.

It's also definitely not the water pump as I verified the pump is off and visually inspected the pump and utility bay (furnace and water heater). The sound is more muffled from the utility bay so it's originating from the walls higher up in the coach. I thought it might be water pipe vibration but the noise will occur when no water is running. I turned off the water supply and depressurized the water system with no effect.

On the exterior there is nothing loose on the roof or slide outs. At this point I'm beginning to believe it may be caused by the wind affecting the tank vents on the roof. I'm really at a loss though. It's noisy enough to wake me up at night. Any ideas of what might cause this?

It's not the Fridge vent flap or Dryer vent flap, if you have one??

No I have a residential refrigerator so no vent and the dryer is on the other side of my coach. No noise coming from it.

My best guess is the microwave vent, as that's what ours sounds like in the right wind.

I would agree with Andy, the microwave vent flapper.

I don’t think it’s the microwave flapper guys as I really can’t hear the noise in the kitchen near the microwave or outside near the vent. It’s also a very fast flutter sound.

I’ll listen to it again once the wind returns. The noise is loudest in the bedroom at the shower wall. So strange.

Do you have awning toppers installed on your bedroom slide? They have been known to flap in the wind and can cause that high speed flutter that you are hearing.

We have a vibrating type sound coming from the kitchen sink when its very windy. Figured it was the wind as it hits the tank vent. Now I actually think it is the Hepvo valve fluttering in the drain line. The vent is allowing pressure to build up in the tank and its only way out is the sink/shower drain.

Rick

No slide toppers on my coach. Rick I think it just might be vent related as you described but not in my sink. Everything is working ok and I've got no leaks or anything but it is an odd noise that I'll probably just have to get used to when its windy outside. What I find so odd is the high frequency of the flutter. Its very uniform and rapid. Again the closest way to describe it is like a water pump cycling on momentarily. Perhaps I can see if I can record it.

there is a drain vent in the kitchen sink and I would guess under the bath rm sink also. my guess Is the holding tank roof vent and basin vents in the coach are balancing air pressure. You may be able to stop that with the roof vent that has a directional hood that turns with the wind. you remove the little exiting cap on the roof vent and put these vent in place of the cap.
https://www.etrailer.com/RV-Vents-and-Fans/Camco/CAM40595.html?feed=npn&gclid=EAIaIQobChMIuKvcp5bz3gIVBJ6fCh0B8Ax8EAQYBSABEgK_lvD_BwE

I have noticed the flutter in my coach recently in the high wind , or actually wind in certain direction. Mine was happening by the bed and would wake me up. So one night when the wind picked up about 0300 I decided to go out and look( since woke me anyways). It took me a while to find the problem. What the problem was on mine is the seal around the slide. I noticed the top flap of the seal was just sitting on top. On my last RV that seal was glued to the seal on the side making it a one piece. But this piece on my bed slide was not glued to the side one and I could see it barely moving and when I held it down the flutter went away on mine. So I'm thinking they use some kind of glue to stick the top seal to the side seal to make water tight. Not sure what glue to use to fix but that's what the flutter is in mine. I put some tape to make it stop for now since it has been cold. Hope ths helps finding your flutter

When it's very windy, I get an occasional flapping noise, it's coming from the sheet metal bottom piece on the slide, I think RW missed some caulking, it allows the bottom piece to move in the groove that connects it to the upper part. I haven't got around to caulking it to prevent the flapping.

I have noticed the flutter in my coach recently in the high wind , or actually wind in certain direction. Mine was happening by the bed and would wake me up. So one night when the wind picked up about 0300 I decided to go out and look( since woke me anyways). It took me a while to find the problem. What the problem was on mine is the seal around the slide. I noticed the top flap of the seal was just sitting on top. On my last RV that seal was glued to the seal on the side making it a one piece. But this piece on my bed slide was not glued to the side one and I could see it barely moving and when I held it down the flutter went away on mine. So I'm thinking they use some kind of glue to stick the top seal to the side seal to make water tight. Not sure what glue to use to fix but that's what the flutter is in mine. I put some tape to make it stop for now since it has been cold. Hope ths helps finding your flutter

Thank you Jeremy. This sounds like the most plausible explanation for what I'm experiencing. It's loudest near my bed at the slide wall. I'll check my seals. It sounds to me by your description that the horizontal roof seal and the vertical wall seal should be glued where they meet?

My coach has the slide within a larger slide too so that could exacerbate the issue.

Our MB does the same. The kitchen slide is not centered in the opening so one side has a larger gap. Its this gap on the side next to the fridge where the wiper flutters. It doesn’t take much wind for ours to flutter.