vent/register noise

[knightonbaldmountain]

I recently purchased a 1999 Fleetwood mobile home. I don't know if the clinks and clunks I hear from the registers while the AC/furnace is running are normal. But what is particularly upsetting is that I hear a loud noise or two(a snap, or pop) coming from one or another of my bedroom vents WHEN THE AIR IS TOTALLY OFF! It only happens in early morning, and seems to be related to the outside temperature rising, etc. If it is agreed that it's not the pipes, what else can it be? A contractor suggested tightening "lag bolts"? under the house. I've tried putting firring strips under these registers to "brace" the ducts. No luck. Also, of course, I've tried running the fan constantly to pressurize the ducts. Again, no good. An AC/heating man said it's like looking for a needle in a haystack, because the problem may not necessarily be located near the bedroom. Am I out of luck/options?

[Sylvia]

Is it in any particular time of year? Could it be rodents? I had birds in the spot at my roof peak for awhile and I couldn't figure out what the noise was. It was only in the mornings while I was getting ready for work that I heard it. I'm sure they made noise other times but I was always gone during the day.

[rmurray]

Fleetwood has all metal ducts...often folks complain about poping sounds that are from expansion and contraction....Short of replacing the ducts (or the home) I have never heard of a way to get rid of these sounds...