Drip coming from downstairs apartment air conditioner.

Okay. I live in an apartment on the third floor. When the neighbor downstairs turns on his air conditioner I get a loud drip I can hear in my air vent - sounds like it's dripping onto metal. There is no water anywhere, it's in the wall. So, of course, I tell the manager and he thinks I'm imagining it. He said he had the A/C guy look at it and they don't know what it is. They haven't heard the drip even though he told me he turned on the downstairs neighbor's AC and then came up and listened for a drip. I told him I am going to text him next time I hear the drip.

Do any of you know how this is possible? Is the manager just treating me like a dumb blonde and not taking me seriously? It wakes me up when it comes on at night. It is driving me mad. I don't know what to do because I don't think the manager believes me or he just can't be bothered really looking into it.

I also sometimes think he wants me to move because it's a rent controlled apartment.