97 Town Car,No Heat

Summer before last I bought an abused 96 Town Car with several problems none major, with one exception. The blend door actuator needed replacing, so I pulled the dash and replaced it cause I couldn't stand that tic, tic, tic, well that stopped the ticing, but it still will not switch to heat unless I set the temp comtrol on 90 and start pushing buttons, sometimes it won't take 5 minutes and sometimes 30 min and sometimes I just give up. If I back off the temp it will reach a certain point and switch right back to cold.
I don't hear the tic, tic of the blend door actuator, so what else could be keeping the heater from working? I have run the self test on the EVAC, no codes.
Any help will be greatly appreciated.
Many thanks,
Frank aka crazyhorse357

Does the engine reach normal operating temp? Are the heater hoses hot? Blower motor works? There are a couple of temp sensors, I could give you the resistance specs? I can't tell if the temp control door is operating like it should? Could be an issue with EATC module, whatever they call it?

Emgine at normal operating temp, both heater hoses hot, blower motor works fne.
I have even flushed the heater core, radiator and every hose that pertains to the cooling/heating system. Is there any way, that you know of, to test the EATC module, I don't know if a new oe could be found and if I get one at the junk yard there's no guarantee it will work and they don't refund electrical parts. I could buy 10 before I found one that would work.

I know you said no codes, but, can you communicate with eatc?

What does the outside air temperature display? Is it accurate within a degree or two? My OAT sensor went bad on me last winter, reading 70+ when it was well below freezing. This caused the A/C to turn on when I had the system set for 72 degrees so heat only came on when I set it to 90F and operated the fan speed manually.