Sticking thermostat could cause this. If the thermostat is stuck open, it never gives the engine a chance to fully heat the coolant. Follow the top radiator hose to the engine, remove the hose and remove what it hooks to and there's your thermostat.
if the blower motor works most likely heater core is bad. need more info
It could be that your head gasket is blown.
the reason for water coming out from under the dash is that a hose could have broke or you have a problem with your heater. your heater works off of the water in the radaitor and since it gets hot from the motor well it serculates threw the heater and that's who your heater works
That or the thermostat.
could be head gasket problem. does your heater work? might need heater core , clogged up. do compression test. or bypass heater core and see if that works.
If it now works it could be a bad connection to the sprayers.
Eventually heater will stop working when coolant level gets low enough. Pressure test system to determine where leak originates
Toaster above is what they are looking for since it has elements like a heater but one could argue an electric stove works the same way-
if engine seems to be over heating or getting hotter i would change the thermostat its cheap about 10 bucks and not to hard but if its not that than it could be not enough anti-freeze or heater core
Maybe low coolant level
The rear defrost is electric. The heater works off the hot water in your radiator running thru it and a fan blowing the heat into your compartment.. check your thermostat, it could be that your heater core isn't getting and water to it, that is were your car get's it't heat from, if not that it could be lack of water
Get the air out of your heater core.