The freezer is working but the ref is not

Question

I am in the philippines and 2 different mecanic could not identify the problem. When the unit is disconnected for 12 H.or more and plugged on again the ref start working good for 2 to 5 days and then the ref stops again. This happened several times .same ice was find between the coils and when dissolved the ref was working again. A mechanic changed the thermostat ,but it did not solved the problem. I am a senior citizen and in this very hot wheather the ref is vital for me and also to keep my medication cool . Please help and advice. Thank you .