Hi Barry,
I had some problems last year with my fridge. I have a 2004 model, with the Adler-Barbour unit.
The compressor is located below the dry storage locker, port side in galley.
Inlet for air is under nav station. Simply take off louverd panel and vacuum the filter off.
When you have access to the unit there is an aluminum control box. It has LED lights
that will give you a sequence code that should identify the problem. BTW, you can get the referigerant from Autozone. I think I have the manual on my iPad, and could email it to you.
My unit had a bad thermostat, I jumped it out and the compressor ran. Then added R134.
Any questions you can email me.
Good luck