96 Bonneville NO HEAT

I have got a 96 Bonneville 3.8L with 120,000 miles

I don't drive the car but here's the problem, the blower seemed to intermittently stop working, stopped working, I would fool around with the blower, it would work for a week, then stop again and start again.
It seemed to be a bad motor.
I had 12 volts at motor, when on high and good ground.
Before replacing the blower, I noticed the car doing something different.

After you start the car the heat will blow for 1-2 minutes
then without touching anything the digital reading for control unit will begin to flash, as it is flashing the temp starts turning to cold air.
about 3 minutes goes by, the display stops flashing and only cold air will blow.
As this this happening I can hear what sounds like the the blend door turing to cold.
If I turn the car off and restart, the process starts over again, will start off hot then go to cold.
There is no issue with coolent problems, temp gauge for car is normal.
The mode doors all work good, will go from floor to dash to vents without any trouble.

Has anyone come across this, or have any idea what I should be checking?

Does this display flash some kind of a code? It only flashes, does not show different numbers, or anything

I don't know how to check, or what to be checking.

Thanks in advance for any replies.