Lots of questions there to address.
(1) Is it normal to hit 102c idling at 90F outdoor temp without AC operating?
- Yes on a 30 year old car. Sometimes people blame the regular fan clutch for not operating properly, sometimes radiator is blamed for not allowing enough coolant flow at idle, etc.
- If I were you I would just lower your electric fan trip temperature to be something like 95c. You can add a 1.2K ohm resistor in parallel to the temp sensor on the cylinder head. Works pretty well.
(2) AC refrigerant leak.
- Is yours converted to R134 or is it still R12?
- In either case check your high pressure house for wetness. If it is wet, read my post on the matter for a quick fix that will only cost you $10. Mine has stopped leaking with that temporary fix.
Everything seems to be operating correctly aside from the aux fan low speed. I did see where you can simply buy a lower temp sensor so might try that.
Converted to r134 at some point. When I bought the car last summer there was some AC, after winter I had nothing and after a can of refrig. its "working" again. Found what looked to be refrig. on the plastic panel under the engine so assuming there's a leak there somewhere.