An electric heater might blow cold air because the thermostat is set too low or is not working properly, the air has not had enough time to warm up yet or there is leaky or blocked duct work. Most of these are easily determined and corrected by the homeowner.
Even in warmer climates, an electric heater is welcome on chilly nights. If the heater is blowing cold air, one of the first things to check is the thermostat inside the house. If the temperature on the thermostat is too low, then the air will not be warm. Sometimes, the batteries in the thermostat are low or not working at all. This will also cause it to malfunction, causing the heater to blow cold air, or perhaps none at all.
Another thing to keep in mind is that the air that is initially blown out by the heater will not immediately be warm. This is especially true if the attic has been exceptionally cold. Just as with warm water coming out of a faucet, the air coming out of the vent needs some time to warm up. If the air is not warm after a few minutes, this may indicate a problem.
Leaky or blocked air ducts may impede the flow of warm air. Leaky ducts cause warm air to escape into the attic instead of making its way into the home. Blocked ducts prevent the air from entering the home at all.