Stuck thermostat or defective water pump.
Most likely this is the result of a stuck thermostat.
put coolant into my over flow car was running hot and the coolant erupted like a volcano on the side of the over flow
Check your antifreeze/coolant level in your radiator. If it is "low", there will not be enough coolant to "flow" through the heater core, to produce any heat. If it is low, refill your system with the proper mixture of coolant and also check for any coolant leaks.
Coolant overflowing from a 2003 Cavalier overflow tube usually indicates a blown head gasket. Check the cylinders for proper compression to confirm a blown gasket.
over heating ,bad radiator cap or blown head gasket
What?! Until full! Start the vhicle, run for 10 inutes to enable the thermostat to open and the coolant to flow. Add the proper mix of coolant to fill the radiator to the bottom of the neck. The system will be sufficienty full
The presence of the valves usually restrict the coolant flow into the heater core.
It might be clogged, thus not allowing enough flow It means that the excess coolant is going where it is supposed to. The coolant expands when hot and goes to the over flow reservoir.
Heat will flow from the coolant to the air The coolant will absorb the heat from the building.
the thermostat
The heater would not be working on a 1990 Dodge Grand Caravan if the heater core is damaged or blocked. Hot coolant from the engine must flow through the core to allow hot air to pass into the cabin.
Your thermostat is probably stuck preventing the flow of coolant to the radiator. This is an inexpensive fix.