Hoping someone can toss me some advice...I'm pretty clueless when it comes to HVAC. Anyhow, I have a newish house (about 3.5 years old). I think my AC system is a split unit. There's the outside unit and another unit above my garage. Anyhow, the outside unit, starting about a week ago, is LOUD when it runs now. There's no screeching or odd noises...its just a lot louder than it was in the past. What could be causing this and do I need to call someone out to have a look at it? For what it's worth, it is working...house is warm.

Not a professional.... Sounds like a heat pump. Could be that its in the defrost mode when you hear it being louder, you tell this by the outside fan will not be turning when its in defrost. There are some experts on here that will ask more questions like if its gas or heat pump etc..

Does it do this consistently when running or just randomly?

Heat Pumps go into defrost cycles periodically to thaw any ice/frost build up from the outdoor coil. With the way the temperatures have been, they will go into defrost a lot more often then normal conditions.

Thanks. It runs almost constantly (its really cold out) and the fan is running the whole time, if that helps. The unit is 100% electric...I miss the gas unit I had at my last place.

So is the noise present 100% of the time when the unit is on and heating?

Yes

Interested in this thread. Mine has started doing the same thing. It also, for lack of a better term, farts when it cuts off. Makes a weird noise phhhhhrrrrrttt noise when it turns off.

Without hearing the noise it would be hard to tell you what exactly it is.

If it's making a noise a lot louder then previously and sounds like it could be a "damaging" sound I would probably have it looked at- just to be on the safe side. Most companies charge a diagnostic fee of 60 bucks +/-.

If you have a way of recording the sound, post it up and we could give you a better guess.

Noise issues are hard to guess at with out seeing or hearing. My guess would be that you may be hearing the defrost cycle initiating in and out and may be hearing the reversing valve shifting back and forth.

One thing to consider on noises changes in the outside fan is the air density, air will be so thick and dense and harder to move with the fan. It will actually pull more amps in weather like this due to the density. The ummmph sound is usually associated with the reversal valve changing position getting ready for the defrost and by reversing flow paths.

Sounds like the reversing valve opened in the beginning stage of defrost.

Do you live close to Huntsville?

Yes, I'm in Huntsville.

I took a quick video in the dark...not sure if you can tell anything or not. Phone was pretty close to the unit...

You can download the file here: NOISE

Is Is a buzzing sound? A squealing sound? A hissing sound? Answer this and it will help to narrow down the problem

Not really a hiss or a squeal...more of a buzz. Almost just sounds like it always had...just a lot louder (maybe a rattle?). For what its worth, it is a Goodman unit, and I've read that they are loud units. It hasn't been loud up until this point, though.

If I had to put my cards on the table, I would say you have a contactor chattering seeing how it's still running, it's a easy fix. Try this, shut off the power to the outside unit at the disconnect, set the t stat to cool or heat, see if you still hear the same noise outside... if so you have a contactor going out which is what I'm guessing

Set it to cool.... and crank it down as low as it will go, if it's a heat pump set it as high as it will go. Just kill power to the outdoor unit and see if the noise is still there

Heat was 'on' on the thermostat...went to breaker in garage and killed the 'heat' breaker. All loud noise stopped (outside unit died). Flipped everything back on and noise is back (took about 5-10 mins for heat to come back on). There was a very faint "airy" sound at the outside unit when it was off...

If it's that loud its either the compressor or a cover or something vibrating. if the coil is really dirty the fan can't pull and cavatates/vibrates. Get a piece of hose and put one end to your ear and the other to the compressor etc to see if ypu can isolate where its coming from.

Replace the contactor and be done with it, I would go back with a 2 pole 30 amp contactor with a 24 volt coil, common part at any hvac supply store or Grainger etc..