Please bear with me, we’re extremely new to this. I’m just trying to help out my husband while he’s away. We recently bought a property with about a 15 foot deep pond on the property. Everything has been running smoothly and all of a sudden it started running incredibly loud. We noticed that only one of two diffuser plates are working in the water. Honestly I have no idea where to start. I would assume something with the motor of course, but no idea.

Very possible that the compressor motor bearing/s are severely worn. The unit could likely stop soon.

What’s the solution to this? Replacing the entire compressor? Can we just replace the bearings?

It will cost about as much to replace the motor bearings as if you buy a new compressor unless you have a friend that is a good electric motor mechanic who works cheaply. Time and materials are costly. Replacing the bearings and you still have a used worn pump. It could make a good back up compressor.

The other thing that it could be is that the seals are going bad on the compressor and it is letting it bang at Top Dead Center before going back down.

Like Bill said, it will need to be rebuilt or replaced. I know how to rebuild Thomas, Gast and Brookwood Compressors, I have no idea where to get parts or how to rebuild Airmax compressors. I'd suggest calling them and see what they recommend.

Just an update. So right now only the fan is running. (Airmax PS20)