Heater is blowing cold air and cooling fan is on when it is freezing outside

The engine cooling fan or the heater fan?

The speed of the engine cooling fan depends on the engine temperature, not the ambient temperature.

COULD BE THE "DEFROST MODE" OF YOUR HEATER

"DEFROST", OR ANY SETTING USING "DEFROST" OFTEN TIMES ALSO TURNS ON YOUR A/C COMPRESSOR IN SOME CARS

IT DOES THIS SO THAT THE EVAPORATOR CAN REMOVE THE MOISTURE FROM THE AIR BEFORE THE AIR IS BLOWN AGAINST THE WINDSHIELD

THIS MAY HELP IN FAST FOG REMOVAL FROM YOUR GLASS

I'VE NEVER HAD A PROBLEM W/ THE SIX CJs I'VE OWNED (THEY DID NOT HAVE A/C)

BUT ANYWAY, WHAT I'M GETTING AT IS YOUR FAN SPEED MAY ALL DEPEND ON THE "LOAD" PRESENTED BY THE A/C BEING ON, WHILE IN DEFROST (OR COOLING MODE)---COLD ENGINE OR HOT, WITH SOME VEHICLES, MERELY FLIPPING THE SWITCH MAKES THE A/C COME ON AND KICKS THE FAN UP A NOTCH TO KEEP IT FROM OVERHEATING.

YOUR TURN

THE MEDIC

The fan on your vehicle is a clutch fan. It is designed to spin faster based on under hood temps. However, they go bad and can spin full speed all the time or not spin fast enough. If it should like a plane, check that first.

Carsonxmitchell: Look the fan over at the center of the fan. You will see aluminum cooling fins. Check for the appearance of moisture. Grasp two opposing blades and wiggle them front and back. There should be no play. If you see leakage or there is play, replace the fan clutch which is between the actual fan and the water pump.

The AC compressor clutch having a short could be an issue IF the vehicle has an electric fan since the electric fan is switched on full time when the AC is on.