When turning on heat after a period of using air

You need a fun motor or a capacitor for the fun motor

Since you have two thermostats that operate the heating unit and the fan, and the fact that neither will turn the blower on, I would suspect the furnace/ air handler. Turn the thermostat to heat and see if the heat and the fan comes on, if it does operate normally in heat, the fan relay or the high speed on the blower is most likely the culprit. (If the furnace is equipped with a circuit board, the fan relay is integral to the board, if it an older furnace it has a separate fan relay). If it does not operate normally in the heating mode, verify power to the furnace, see if the flame comes on, if it does: the fan motor, circuit board or the fan relay are most likely the cause. hope this helps!

Wish I knew how old your furnace is. Let me answer your question directly. In the heat mode the fan runs independently from the air conditioning fan relay. Its either brought on by time or temperature. An old furnace will use a fan and limit control that uses a coil to sense the heat exchanger temperature and turn the fan on or off. Newer furnaces use a timer on a circuit board. 20 years or newer Ill bet its a timer board. Follow the blower motor wires back to the component and ill bet that's the culprit. Hope it helps. Good luck.

Problem could be the thermostat setting in "fan on" mode. Thermostat could be shorted between Y,R and G. Fan relay points soldered together or main board shorted.

try to replace your thermostat and conduct observation with your furnace if happen again after replacement of thermostat furnace also damage.

Hi,
The solenoid vlave is stuck in the on position and will need to be replaced...

Here is a tip that wrote about how to buy heating and air conditioning parts online.

How to find Air Conditioning, Heating and Furnace parts online.

heatman101

First HACR is heating, air conditioning,refrigeration. So in other words you could use it on an electric furnace or air conditioning.
IS this the main breaker for the panel? or for and electric furnace. I'm assuming its for the furnace, perhaps back up heat for heat pump. See if there is another disconenct on the furnace, turn it off and see if the breaker resets. IF so you have a short or overload in the furnace.
If' it IS the main for the panel, turn off all the other breakers in the panel, and try to reset the breaker. If that works, turn the other breakers back on one at a time. IF it "POPS" then it is tripping. Don't keep resetting, find the problem.

Actually yes! You can install electric elements in the plenum that turn on by your thermostat. The convection blower from the furnace can be used. You can also install a heat pump system that will give you both heat and air conditioning.

An explanation....

When in the heating mode, all heat pumps are dependent upon the outdoor conditions to remove heat energy from the environment and turn it into useful heat for your dwelling.

Heat pumps operate more effectively in temperate climates (as in southern states) and if it's as cold as you say, then the furnace is coming on to add auxiliary heat to the space to make up for the lack of heat being supplied by the heat pump. This is normal.

Some heat pump systems are or can be equipped with a control known as a "low ambient cut out" and/or "motor master" that prevents the heat pump compressor from operating and slows or stops the condensing unit fan when it's too cold and risking potential compressor damage. When it's in the single digits outside, a heat pump is only marginally effective. and usually requires auxiliary heat (your furnace).

If the furnace keeps operating when it's in the 30s or 40s, you may want to have the system examined by a competent service technician. As always, the outdoor condensing unit should be kept clean and the furnace filter should be changed no less than monthly, unless you have an electronic air filter.

You,ll need to open the furnace and observe the led lights on the comtrol board the is a chart attaced to cover. If it is in lock out mode the fan runs. To reset turn off at tstat.the turn the power on at the furnace, set tsat up, observe furnace. First you should hear a small fan then the glow of the ignitor then the opening of the gas valve and flames 10-30 seconds then the big fan.