AC blowing from cold to hot

[BMG Coach]

The roof air forward unit runs 24/7. It runs cold then warm, Turning it off doesn't change anything. The rear unit runs as it should and also maintains the thermostat temp. Any help?

[77newell]

Is the compressor running 24/7 or just the fan? If the compressor is running all the time and turning it off, waiting a half hour or so for any ice in the evaporator coils to thaw doesn't do it, then you've got something massively wrong in the Freon circulating system that I just can't figure out.

If the compressor is cycling with the hot and cold then I would suspect something with the thermostat circuit. I had something like this once when the thermostat didn't always make contact but then later would, a new thermostat solved that one.

[NewellCrazy]

Sounds like you may be due for recharge.

If the compressor runs without any refrigerant it will burn up.

So they use a pressure switch to stop the compressor once the refrigerant gets below a certain level. The refrigerant is being moved from the low pressure side to the high pressure side.

When you are low, there is enough refrigerant to start. However, once it starts getting cycled through out the entire system, it drops below the minimum pressure needed to keep the compressor running without destroying it........

That's just my take on your symptoms for what its worth.