Knocking sound when A/C or heater is running

I have a problem that may sound strange, but it drives me crazy. Often times when my air conditioner or heater is running, there will be a faint knocking sound just above the light fixture in my bathroom. It's not very loud, but I'm a very light sleeper so any sound at all will keep me awake.

I can't begin to guess what could be causing this sound, or even what the connection could be between the A/C and the location of the noise, but it's happened often enough that I'm certain that such a connection exists. And I can't even call for someone to check it out because it's intermittent, and also because without a clue what's going on I wouldn't even know who to call.

Please let me know if you have any thoughts or if you need additional information. Thanks.

 

Very likely thats where the air handler for your system is, but you haven't given us much to go on. Could be a slightly off balance fan or a collection of dust and crud on the vanes.

You may even have a suspended air handler that is moving slightly.

You need to describe your home a bit. Is the attic above the bathroom? Do you have access?

As to the sleeping thing....have you tried a white noise generator? I have a little clock radio sound machine that I will use sometimes, really seems to help.

 

There is indeed an attic above the bathroom. I took a look up there once, but that particular spot is covered with insulation. I never actually went all the way up there to investigate.

 

Vibrations can travel quit a distance. Since it's intermittent, I'd suggest you try to identify when and where it's actually occurring before you call anyone. That will probably mean climbing up there and carefully getting near the location. You could find that just putting your weight on a truss or rafter makes it stop.

You might also take some sort of padded pole or board and push up on the area in the bathroom. Amazing what you may find to help you narrow it down.