[deniseO30]

The Refridge may be wired to run right from the battery bank. First thing you should check is the condenser fan on the unit. I've a feeling it's broke, bad bearing or fell apart. The Refridge would still work without the fan.

I'd suggest you get a bit more personal with your boat and learn all about her systems.

Jus sayin...

 

[deniseO30]

Maybe something else is humming? ON shore power I think the Refridge would still be on 12 volt if it's AB. I think some boats hum if the polarity is wrong on the AC coming in. Bilge blower maybe? I hate to think the comp is bad.. it can happen but extremely rare for a piston related type of failure on the inside of the "can" Try the old "hose to the ear and on the noisy part trick"?