Mazda Millenia heating/cooling issues...

[DA-MAX]

The car in question is a 1997 Mazda Millenia. The first symptoms I noticed were the heater not heating(digital climate control) up enough even on the full setting. It would only blow cold air. The car would reach and hold operating temp, but cold air would continue to blow.

So I began to diagnose ad fix...The display on the HVAC dash control unit was screwed up, so I changed that($5 from junkyard) just because. I changed the fill neck radiator cap as well because the rubber seal was worn. At the same time I flushed the heater core, lots of "belching" and bubbles, a good bit of heat returned, but only when climate control was set from ~87-90*(all this done in mid Nov.). I bled the system out by letting the car run on an incline with the filler neck cap off until most of the bubbles were gone. The fans never kicked on most likely because it wasn't that hot outside is my guess. The car ran fine and the heat lasted until about this week(of course when it has dropped to 12-20* outside ).

Today the car has little to no heat even after reaching operating temp. And once at operating temp sometimes when at a stop the gauge will slowly creep ever slightly above normal.

some observations:
-Coolant level appears fine
-no visible coolant leaks
-heater hoses are NOT very warm to the touch
-top radiator hose is never "firm" even after car has been running for long above operating temp
-both raditor caps appear in good condition

only things I can think of could be: bad/clogged heater core or air entering the system somewhere. I would say bad T-stat, but the car never drops from operating temp(ie-stays cold) and only slightly goes above normal.

any ideas, suggestions, help would be more than appreciated cause I'm puzzled