I have installed the 18.104.22.168 instant client on a developers PC. I have also installed the odbc, sqlplus and the odac libraries into the instant client home. I have set the TNS_ADMIN and PATH variables to point to the correct location. This I can prove by connecting successfully to my database from sqlplus in the instant client home.
My issue is that when the developer tries to connect through the application he receives the ora-012514 error. There are a number of full clients previously installed on this machine. How do I set the instant client to be the default. I'm guessing that this is the issue.
I took all references to old clients out of my path and this has resolved the issue. I'm sure why this happened as I had the instant client as the first entry in the path. Anyway it's working which is the main thing.