Okay, recently the ECC readout began flashing the temperature about a minute after vehicle startup, then after a couple minutes of flashing, the temp settings quit flashing, and ECC displays the outside temperature and no longer flashes until the cycle is resumed when vehicle is shut off and restarted. To summarize; start the car, ECC readout is stable and does not flash, 1 minute later the ECC readout starts flashing temperature, about 2 minutes later the ECC quits flashing and is solid/stable readout.

All functions of the ECC appear to work normal, the manual and automatic settings, defrost, dash vents, floor vents...fan speed, temperature settings, etc...However, the PROBLEM is the heater system is not blowing hot air through any of the vents. Fan turns on and air circulates, however is cool and not hot.

Checked the heater hoses to the heater core, and both hoses (in/out) are hot to the touch, and too hot to hold on to. Vehicle engine temp stable at 200 degrees.

Interesting to note, when the vehicle is warmed up and then shut down and immediately restarted, the heater will circulate hot air for maybe 1 minute when the ECC is not flashing, then the ECC will begin flashing and the hot air will turn cool during the time the ECC is flashing, and the vent temperatures then stay cool even when the ECC quits flashing.

==Couple Questions==
(1) Is there a way to determine what the ECC flashing code is, and how to clear it? Or maybe its not relevant.
(2) Any suggestions what might be causing this loss of heated air circulating through the vents and what or how to fix?

Thanks.

Issued solved. Was the Airmix Actuator Control/Blender Door Actuator. Broken gear inside the assembly once I pulled it apart. Read a lot of posts about this before taking off. Followed general procedures of removing from underneath the passenger side, etc...no fun, but done and works again.

ACDELCO Part # 1571923 **#16141822}
ACTUATOR,TEMP VLV w/A/C AUTO ELEC CONT(C68)