I'm assuming that you mean the compressor is running all the time? The a/c compressor should run in the defrost position automatically, even when it's cold out. I believe it is to 1) reduce humidity and clear condensation off the windshield, and 2) to keep the compressor limber all winter -- otherwise it wouldn't be used from September till May and it might not work when you need it then.

I don't think the compressor runs even on defrost when it is below freezing, but I could be wrong on that.

Possibly your compressor is stuck in defrost mode even if you're running the heater. Try pressing the a/c switch on & off a few times while the heater is running. That might get it to cycle off.

Is your engine running in the normal temperature range? If the engine is running cold it could be that a thermostats is stuck open so the engine isn't getting warm. If the engine is running hot it could be that you're low on coolant and the hot coolant isn't making it to your heater core. Worse case would be a failing water pump.

I'm no mechanic, just a Patriot owner like you. There are others on here more knowledgeable than I am. Keep checking back and give more members a chance to respond.

 

The most common cause of ambient air coming out the vents and not heated air is a bad temperature blend door motor stuck in the cold position. Sometimes you can get it free by turning the temp dial back and forth from heat to cold and putting the air path to floor. Otherwise it may just need replacement. Less common is for the heat/ac control itself to go bad. Try verifying that the air paths are all working by placing it on floor, then feel air only blowing on the feet and nothing out the dash or defrost vents, repeat for dash vents, then defrost.
When you stated the ac works when cold, if you meant you can visually see the compressor pulley turning, this is normal as our vehicles use a variable stroke compressor instead of a traditional magnetic clutch compressor. So instead of just a compressor that is either off or on (100% engagement and freon circulation), the computer can engage the compressor based on temperature and freon pressure and vary the need from 0% to 25% to 50%, etc based on demand. This helps our engines get better fuel economy. So even though you may see the compressor pulley spinning in the dead of winter, internally the computer can set it to zero stroke, essentially letting it freewheel.