Furnace is exhibiting strange behavior and I can't figure out what part has failed. System is set to "Heat", fan set to "Auto", and temperature set to 74. Room temperature drops to 70 and furnace will not start. I move the fan switch to "On". a moment later, the fan starts running and I set the switch back to "Auto". The fan continues to run, and, the furnace heats the house up to the set temperature. Then everything shuts off and will not start again, no matter how cold it gets, until I move the fan switch back to "On". OR I move the fan switch to "On" and leave it there. The fan motor runs continuously but the furnace cycles on and off, maintaining the set temperature in the house, even if I run it this way for 8 hours. Maybe it's the blower motor temp switch but I don't understand this behavior. Thoughts as to what is happening are appreciated. TIA

I am going to move to a new home, and I would like to take my AC units with me. But they are old... 15+ years old. The external unit reference is AE-XM30FR, with 3 internas units: a wall mounted multi split (AE-XPM9CR) and 2 floor standing (one is GS-XPM18FGR, the other looks the same but with a different capacity - 12k or 9k BTUs). In my new home I can only use wall mounted internal units. I haven't yet found anyone who can confirm if I can use more recent internal wall mounted units. Current ones. Any help is appreciated! Thanks in advance