Ill Conditioned Preconditioner

Hi everyone,

I haver been trying to untangle this ill conditioned error with different meshings, which I think is the cause of the error.

The temperature distribution in the soil (from 3D plot group - Isosurface) seem to be reasonable, but with that error, I am not sure if the results are correct or not.

I have attached the file.

Please take a look and suggest what I should do to correct this.

Thank you in advance.