Dealing with a unit that buzzes only on humid days

I've been stuck on this service call where the AC makes a buzzing sound, but only when the air feels thick with moisture. Everything checks out fine with the contactor and capacitor under normal conditions. The customer gets annoyed because it works quietly on dry days, so they doubt my skills. I even tracked the humidity with a meter to prove I'm not imagining things. It points to moisture messing with the electrical bits, but I can't pin down why it's so weather-sensitive. Maybe the wire insulation is degrading and soaking up damp air. I thought about suggesting a dehumidifier, but that seems like avoiding the real problem. Honestly, it's enough to make you question your whole approach to diagnostics.

4 comments

4 Comments

the_jenny1mo ago

Wow, I used to brush off how much damp air could mess with stuff. Then my old radio started crackling only on rainy days, and I found a tiny speck of green crust on a wire connection... it totally changed how I look at intermittent problems now. You tracking the humidity with a meter is smart, that proves the pattern is real. Sounds like you're completely on the right track chasing a moisture path.

the_felix28d ago

Hey, that's a solid point from zara512 about the disconnect switch. I've seen that green crust creep into relay sockets too, where you'd never think to look. It's wild how moisture finds the smallest path to cause the biggest headaches.

zara5121mo ago

I read on HVAC Talk that a bad disconnect switch can hum when it absorbs moisture. (It's a common hideout for humidity gremlins.)

ward.piper28d ago

That bit about the green crust on a wire connection is exactly it. I used to think if it worked fine most of the time, the part was fine. Now I know that little bit of corrosion only shows itself when the air gets wet enough to bridge the gap. You're definitely chasing the right thing.