Indoor fan blowing cold air when on heating

Make sure the setting on the remote is correct . Sun symbol for heating. Make sure the filters are clean. On heating, the indoor unit will 1/2 open the flap but the fan shouldn't start. The outdoor unit should start and if working properly, will be blowing cold air. The indoor unit will open the flap fully and the indoor fan will start once it gets hot then you should feel warm air. If the outdoor unit is blowing warmish air, I would say the reversing valve coil has failed or one of the indoor temp or pipe sensors are faulty. If a sensor fails, a "CH" error should appear on the display.

"Coolant Fan" is not necessarily a common term used to refer to any particular fan in a standard HVAC system. Are you referring to the "Indoor Fan" that circulates the air within the living space???? OR are you referring to the "Outdoor Fan" or "Condensor Fan" that circulates the air across the outdoor coil ??

If its the indoor fan on an air handler that's not running unless its in A/C mode, it will be a faulty heating circuit fan relay on the main control board.

If its the outdoor fan and its a heat pump system the outdoor fan stops during the defrost mode so there is a slight possibility the system defrost board is faulty and stuck in defrost.

A little more information may help obtain a more specific answer.

make sure the filter is very clean. make sure all supply grills are unblocked and open. make sure the indoor fan is blowing. icing coil is normal during heating mode the system will defrost using a sensor. sometimes during cold wet weather the coil will stay iced up. sometimes in cooling mode when it is cool outside 60 degrees or less the coil will ice. low freon will make the coil ice up ,also defrost control not working will cause the coil to ice up

Hello I think it is a faulty defrost interlock or should at least bring on 1st stage electric heat during defrost mode.

The indoor fan will not run at normal fan speed untill the indoor coil reaches 32oC. This is done so that a cold draught is not felt when outdoor unit is not running. Check to make sure the outdoor unit is operating. If the outdoor fan is running but there is no indoor fan after 5 mins then you must likely have a gas issue or a fault compressor circuit.

Yes. Heat pumps have to go into defrost just like a freezer when the temp gets too cold outside. The heat pump will temper the indoor air electric heat.

Yes.Think of a heat pump as a A/C in reverce in cool indoor coil is cold&outdoor coil is hot.Naw indoor coil is hot &outdoor coil is cold&fan is pulling in cold air from outside.its going to iceup& go into defrost cycle.If your unit has a timed defrost every 30,60,or90min.(witch ever yours is set for)Defrost control board checks a sensor on cond.coil,if it is frozen unit goes into defost.You will here a swishing noise,iis the reversing of refrigerant.you will also notice the outdoor fan is not operating&at termanation of defrost fan will blow out steem.the other metod is on demand defrost.when coil freezes unit defrosts.

You need to replace the defrost board and sensor

this happens when the outside temp is low, asthe outdoor unit blows cold when in heating (reverse) then the unit goes to pre def to avoid it freezing. You should hear a whoosh this is the heat being blasted to the outdoor unit to defrost it, then the heat has to build up again before the indoor unit fan runs up again and blows heat. Mine does the same every 20 mins or so (its -2 outside) brrrr
Leigh

Double check your wiring .if the indoor fan is not blowing then you either have an electrical issue OR bad blower motor .