Compressor is making a loud grinding noise

Graham_2024

Would you help troubleshooting this?

Inside coils are from 2012. Outside is either 2012 or ~2001. I notice that in high load scenarios the compressor will make a very loud grinding/honking noise in the first 1 minute of operation. After that it seems to run fine until it satisfies. I checked the amp draw and the draw seems to go down from about 17a to about 12a during this sound event and then returns back to 17a. I replaced the run capacitor like for like in the spring but otherwise we're new homeowners and don't know the history. Attached audio (around 1:30 ish the sounds peaks)

Air conditioner.m4a.zip

HVACNUT

Sounds like either non condensables in the refrigerant circuit or the compressor is chugging liquid. Time to call a pro.

Graham_2024

What will a Pro do? Thank U HVACnut

mattmia2

are the bushings the compressor sits on rotted out so it is metal on metal or 2 pieces of tubing touching and vibrating sometimes or a piece of the cabinet vibrating? if you hold various things still or wedge a piece of foam or cardboard between them does the sound go away?

EBEBRATT-Ed

I agree with @HVACNUT. Could have liquid in the compressor on start up. Check to see if you have a cch and if it is working. Could be overcharged as well. check filters in air handler or furnace and make sure they are clean and the blower is moving air.

mattmia2

would it need a crankcase heater this time of year? it has been 90 here in michigan the last couple days, don't know where the op is.

don't underestimate the sounds you can get when the compressor or the tubing touch the cabinet directly.

EdTheHeaterMan

https://forum.heatinghelp.com/discussion/comment/1898352#Comment_1898352

What a professional will do is measure the refrigerant pressure and the temperature of the refrigerant, and compare those readings to the normal values shown on a chart located inside the equipment, on a data sticker, or in the installation manual for that particular model. With that information, the professional will be able to determine whether the system has too much refrigerant, not enough refrigerant, or if a component is failing to operate properly.

At least that would be my first step if I heard that sound. Other professionals might go directly for the "new equipment" approach, since that unit is more than five years old.

Beware of the salesman-technician. If all you own is a hammer, every problem looks like a nail. Their knowledge of how to diagnose and solve problems may be limited, so they are trained to sell new equipment whether you need it or not.

That sound reminds me of refrigerant pressure being released or diverted. Some compressors have an internal relief valve that operates to protect the compressor from being damaged by liquid refrigerant. That sound is also similar to the operation of a reversing valve during a defrost cycle, but that should only occur during the winter while the heat pump is operating in the heating cycle. Do you know if you have a heat pump or is this a cooling only system?

mattmia2

incorrectly configured or wired t-stats can activate a reversing valve at the wrong time too.

pecmsg

That's a sign the compressor super heat is too low. Probably been slugging liquid for quite a while and washed the oil out of the bearings.

Nothing can be done except replace the compressor when it fails.

Graham_2024

Do you know if you have a heat pump or is this a cooling only system?

this is an AC only

Graham_2024

Thank you for all of the comments!

Graham_2024

would it need a crankcase heater this time of year? it has been 90 here in michigan the last couple days, don't know where the op is.

This is in Denver. its been around 90

pecmsg

Crankcase heaters are only needed to keep the oil warm when the compressor is off.