My furnace rattles loudly, but only at night, and you can only hear it upstairs. It sounds like a spoon you accidentally left in a half-speed blender, except it’s a steady beat, not chaotic. It starts when the furnace starts at night, and does not go away until I turn the furnace off. The furnace works and blows hot air while the noise is happening. If you ever watch television, it’s at least as loud as that. It’s impossible to sleep through. Here’s everything I’ve done to diagnose the issue so far:
If I place my ear to the wall at any point upstairs, it sounds as if it’s coming from that exact point, on the other side of the wall. This is true no matter where I test it upstairs, but not downstairs. No matter where I put my ear, it sounds like the source of the rattling.
It’s not coming from the furnace itself. When I climbed up into the attic to try to find the noise, there was no rattling noise even though it was very loud and clear as soon as I came back down the ladder.
This makes me suspect it’s not the furnace making the noise, but something in the duct work.This would totally make sense except that…
It only happens at night. When the furnace blows hot air during the day, there is no rattling. The noise almost seems malicious, like it’s specifically designed to only happen while we’re trying to sleep.
Anyone have any ideas? I’m going crazy. The next step is to just burn the place down and collect the insurance money so we can move somewhere that never gets cold.