THE LOW COOLANT LIGHT IS FLASHING AND ALL FLUIDS ARE IN AND THE VAN DOES NOT OVER HEAT. WHAT IS ACTUALLY CAUSING THIS PROBLEM?

If the heat selector control button is working properly and there is no heat, check level of coolant. Low coolant will be a definate cause of low/no heat. If coolant level is good, you need to check blend doors for proper operation on the heater control assembly

That would be the light that tell you your rad coolant is getting low and you will have one for oil to. check all the fluids.

Your thermostat sound like it is stuck open.
How it works is your thermostat is designed to be closed when your engine is cold.
After you start your car your engine coolant circulates in the engine block.
This helps the engine reach its normal running temperature.
When your engine reaches the normal running temperature the thermostat slowly opens allowing the coolant to circulate through your radiator. the radiator cools the coolant and maintains your engine temperature so your engine does not over heat.
If your thermostat is stuck open your coolant is not permitted to allow the engine to reach normal running temperature. Causing your low temperature reading.
Hope this helps please give feedback good luck FixYa

thermostat

When your not feeling heat coming from the heater it usually means that the coolant level is too low in the radiator. It sounds like you have a coolant leak somewhere which is causing your overheating problem. Fill your radiator and let the engine run for about a half hour with the radiator cap on tight. Then turn off the engine and check for any leaks under the van. If you don't see any leaks under the van then see if the carpeting is wet on the passenger side of the vehicle. If the carpet is wet and it smells like anti-freeze you have a heater core that is leaking. I hope this helps you. :)

Engine coolant temperature sensor.

you may have a air bubble stuck in the system next to the system, or your sensor it bad, I think it maybe under the big coolant bottle

If the temp gauge is reading normal, the lights are flashing, and the coolant level is full, the level sensor in the coolant bottle is the problem. I'm a service consultant for a Saturn dealer and I've run across this many times.

It sounds to me like you're low on coolant. When you checked the coolant level, did you actually open the radiator cap and make sure the radiator is full? The plastic tank you generally add coolant too is actually an 'overflow' or 'reserve' tank. There is a hose that runs from that tank to the top of the radiator so if the radiator gets low on coolant, more coolant -should- run in from the overflow tank. However in practice this does not always work. I have a Jeep that leaks coolant and experiences this exact same problem. Coolant will not run from the reserve tank into the radiator because the hose is plugged up, and whenever the radiator gets low on coolant the temp gauge will go real high and then drop, and the heater doesn't work well. This is because the cooling system of your car is supposed to be a closed system, full of coolant and no air. When coolant leaks out, the space it used to occupy is now occupied by air, which does not transfer heat well. When 'air' is passing through your cooling system, no heat can be transferred from your engine to the heater and radiator, resulting in a hot engine and no heat at the heater. Then when a pocket of water passes through the system, the temperature gauge quickly falls as the water absorbs the heat from the engine. The hot water that cools the engine is where the heater gets it's heat from as well, so when water passes through the heater core, the heater works, but when it's filled with air, it doesn't.

Check all the Fluids Under the Hood. Oil, Coolant ETC..... One of these Being a little Low will Trigger this Light. Please Rate My Response! Thanks!