Hi:
To fix my unit I did replace the power relay but I really believe the fix was simply cleaning the contacts of the sensor that fits in a holder in front of the fins. From the back mine was on the left side. It was during my 2nd attempt to fix mine that I realized the connector & pins for the sensor are of poor quality, they should be gold plated. After using “Deoxit Gold” on the contacts the unit has run without further issues.
If you need more detail for finding the connection (in the steel covered box) please let me know and I will see what I can dig up. I also have a second power relay I bought if you want to try that route.
Tom