My outside HVAC fan runs constant. To prevent more damage I kill power at breaker as needed. The A/c compressor comes on and goes off with the thermostat inside the house. Freezing in the lines is not the problem I am positive of that . I tried replacing the fan relay switch but that was not the problem. When the problem first started the units fan was on for hours and damaged the contact switch so that has also been replaced. It Feels like a sensor croaked somewhere but I am not sure. Any Advice?
The Heat function went out on the outside unit last winter but the heat strips in the attic still work, I had a tech check it over and he said the defrost chip board was the reason. I did not let him work or replace the part when he would not tell me were to purchase a replacement for myself,
By the way it is a Rheem Imperial classic 13 from 1989 with no tag to mention any more
It's a 2 to 2.5 ton split system heating / cooling unit

I would replace the defrost chip board as the tech stated. Without model number of the outdoor unit we cannot find a part for you. I recommend having the technician replace the board if you do not have the means.