Doug: A couple years ago when I had problems with the series 3, you had recommended to me to jump the grey connectors as part of the diagnostic process. The resolution then, was a bad main relay.(I have to see if the 85 XJS has the 2 grey connectors).
Subsequently, during the summer of 2019 I had a situation where the AC system would not turn 'on' and that was resolved with the replacement of the Mode switch which I acquired from EVERYDAYXJ.
In the next week or so I will have a main relay, amp, mode and temp switches (all of which are "KNOWN GOOD") in my hands so I can sub the parts as I proceed with the diagnostics.
Will keep everyone in the loop as I go along.
@Grant: I hope I don't have to go behind the instrument cluster. 3 weeks ago I had it out to get all of the lights working and ended up having to do a lot of soldering back there because there were some broken bits.(Lots of brittle stuff behind the cluster).
I ended up having to (very gently) replace the instrument cluster and it functions as it should now.

 

Thank you all for your inputs.
Blower motor issue resolved: Faulty Mode Switch. Replaced Mode Switch and all is well.
During the process I disconnected and cleaned every connector I touched.
Now on to putting everything back together again.