In cold weather, does not produce heat until engine is under load and on the road. Engine temp is fine. Coolant fine. Could it be the thermostat?

It may be a faulty thermostat that is binding in colder weather.The thermostat opens and closs controlling the flow of the coolant.It almost completey keeps the coolant from circulating until reaching a pre determined temperature opening and closing to maintain that temp.It could be sticking wide open and colder temps thus moving the coolant too fast not allowing it tom remain in the engine block long enough to be heated.

Yes, the temperature gauge should normally stop in the middle, between the cold and hot points on the gauge. When the engine is cold the thermostat will be closed and will keep recirculating the coolant in the engine block until it warms up sufficiently. Then the temperature of the warm coolant will cause the thermostat to open the channel to the radiator to get rid of excess heat, which should stop the coolant from over heating. So the effect of the thermostat keeps the coolant at a fairly stable temperature. When the coolant runs low, it can't transfer enough heat to the radiator and the coolant and engine then over heats. Watch for radiator leaks under your car after you have been driving it. If the coolant goes low again fairly quickly you could have a leak in a hose or the radiator itself.

change the thermostat, sounds like it could stuck open and wont allow the engine reach operating temp, also test the constant control relay module located to the right of the battery as your facing the front of the car, also test coolant temp switch it might be defective and producing a high voltage that would cause the fans to constantly operate no matter the temp. Hope this helps

Just saw your second posting, so the temp is still above normal. Could the sensor
that controls the fan be not reading the heat properly ? The antifreeze/coolant
issue could still be relevant, so I will re-post that info. Tho.
Electric cooling fans will sometimes come on after a vehicle is parked,
(It actually heats up when stopped), but not when it is rolling down the road
because the movement is applying some cooling effect to the engine.
\
If the engine is not actually overheating, then the fans may be working
normally. Also, make sure your water/antifreeze mix is correct by using a
specific gravity tester. It is a tube with 4 or 5 balls, some of which will float
to give you a reading. Contrary to popular belief, More is not better when it
comes to antifreeze/coolant. It needs water to work properly. Too strong a
mix will actually make your vehicle run cold so that the temp sensors and
heater will not function properly. The engine will not achieve proper operating
temperature and may actually damage some of the components by running
it cold, affect timing, spark, etc. This could also cause the symptoms you
describe. The engine would not actually reach the proper heat threshold
until you added the extra demand of the AC heat transfer. But the first criteria
would be whether the engine is actually overheating / or in normal range .
It may be that the colder weather is allowing the sensors to come on a little
later, warming the engine and heater components a bit more than they would
in warmer weather. Would be good to know what the actual coolant temp is.
Could check that with a guage, and also check to see what temp thermostat
you are using. 195 degrees in the winter would be better, 165/180 or so in the
warmer months

Get your radiator and heater core flushed out, if this doesn't fix the issue then your contol damper is probably not functioning like it should. The heater core and radaitor should be able to get flushed at the same time and this is a good thing to do on occasion anyway. Have you check your engine thermostat? this could be the culprit if it is not closing and allowing the engine to heat up.

It is possible that your thermostat is stuck open. Normally, the thermostat remains closed when starting cold, confining coolant to the engine block and cylinder head until it heats up. Once the coolant in the block is warm (usually within 10 minutes), the thermostat begins to open and let coolant flow into the radiator to cool it down some. A properly operating thermostat will continue to cycle until the coolant reaches the operating temperature of the thermostat--usually around 180 deg F. Then the thermostat will continue to adjust its opening to maintain that temp.

Thermostats can get stuck in both closed and open positions. When stuck closed, the engine will quickly overheat. When stuck open, the engine will take forever to warm up--especially in cold weather because the coolant is continually pushed into the radiator and cooled off before it ever has a chance to get warm. Changing the inexpensive thermostat may help correct your condition.

REPLACE THERMOSTAT.MAKE SURE COOLANT SUPPLY PIPE OR COOLANT RETURN PIPE NOT STOPPED UP AND YOU HAVE ENOUGH COOLANT IN THE SYSTEM.REPLACE THERMOSTAT.CRANK ENGINE UP AND LET IDLE UNTIL WARM UP KEEP EYES ON TEMPERATURE GAUGE. WHEN ENGINE THERMOSTAT OPEN COOLANT HOSE SHOULD BE HOT.IF NOT TURN OFF ENGINE.USE LARGE RAG WAIT A WHILE BEFORE REMOVING RADIATOR CAP CHECK TO SEE IF COOLANT LEVEL DROPPING IF SO ADD MORE COOLANT.CRANK ENGINE UP UNTIL THERMOSTAT OPENS UP.HOSE WILL GET HOT.IF STILL COLD CHECK COOLANT LEVEL.ONCE YOU AIR OUT COOLANT SYSTEM RADIATOR HOSES WILL GET HOT SO YOU WILL GET HEAT.IF COOLANT LOW YOU WONT GET NO HEAT.

The reason for replacing the thermostat is improper cooling - not heating. The purpose of the thermostat is to shut off the flow of coolant through the engine allowing the temperature to build. When it reaches the temperature it wants the thermostat opens and allows coolant to flow to maintain the proper temp. Dodge Caravans have a track record for maintaining a low temperature until the engine is at higher rpm. While it is inconvenient in cold weather it it not bad. However, you want to check that your radiator fan is shutting off when it is cold. A fan that is staying on when it shouldn't could cause the temp to stay cooler.

Check the temp of the heater hoses going into the heater from the engine in the engine compartment.
If you have a temp gauge on the dash does it go at least 1/3 the way up the gauge from cold in normal driving.
You can take a garden hose and flush the heater....both ways back and forth then reconnect heater hoses and check for heat.
But.....The # 1 cause of no or low heat is the engine thermostat.
It needs to close tightly to force the engine coolant through the small heater core.

First check your antifreeze level - especially if your car is equipped with the 3.4L engine. these are known for coolant leaks due to failed intake manifold gaskets. Coolant levels that are slightly low can cause poor circulation through the heater core and can "fool" your gauge sending unit into "thinking" that the temp is low when the engine is actually on the verge of overheating.

If the coolant level is OK when you check it, replace the thermostat.