Why is cold air blowing out of a duct and what temperature is the cold air?

I'm having a problem keeping my home warm, I have a gas furnace...and noticed cold air blowing....I checked the registers, warm air blowing, but the cold air registers had cold air blowing out of them. I have to set my thermostat to over 80, but it only registers around 72 all the time....the cold...

Philco central heater only blows cold air when it should be blowing hot air. And it will not stop blowing even when I turn off the heat. The fan is not on itis on auto.

I have hot air central heat and the return duct is blowing out cold air and at the same time sucking in the room air

Our cold air registers are blowing cold air worse than if the windows were open. The hot air registers blow cold air but not as forceful (maybe because they are 1/3 the size of the returns) This only happens when the furnace is off and we are heating with the wood stoves. We have metal ducting...