Frigidaire 9.9 cu ft lights on but no cooling is home

I have this nice fridge but the lights are on and not cooling is going on. It started by going in and out of consciousness (so to speak). It would work for a week, two or maybe even three and then it would stop working for a day or two. Then this became more frequent and the down time was longer. I took it to a guy to fix it and he charged me $35 and said all he did was replace the defrost timer. It worked for three weeks and no it is out again and will not work anymore at all. It has been out for 3 weeks this time. I’m not sure he replaced anything at all, I think he got it to the shop, plugged it up and it started working. I think he then let it run for a week and assumed it was fixed then charged me $35.00 for checking it out. I don’t know but they sent me my money back with no argument at all after I posted that I had paid a guy to fix it and it wasn’t fixed. I didn’t even give their name. That’s what makes me think that. ANYWAY~ It isn’t working, the light comes on so I know it is getting power. Can’t really hear anything running including the fan in the freezer compartment. How can I tell if he replaced it and what should I do next if he actually did?

Unplug the fridge. Remove the wires from the thermostat (temperature control) and connect them together. Make sure the wires are not touching anything else. Plug the refrigerator back and see if it will work.

If it will, replace the thermostat.