It could be low on anti-freeze/coolant. The coolant ratio could be off (especially if there is a leak and you have been adding water not 50/50). It could be the thermostat. It could be the water pump. It could be a plugged radiator or heater core.
Begin with the least expensive and easiest and diagnose deeper until you find the problem.
Do you have any particular car or any particular motor in the particular car? BClear.
You have a blown head gasket.
Car not blowing air or heat
there is no heat inside the car what is wrong ?
Replace blown fuse
the heater core may be plugged up
If everything on your car ( thermostat, heater core, heat controls, water pump) has been changed and you are sure that it all works, check the water flow. A clog or an air bubble in the heat lines will cause coolant to not flow and have no heat output.
You could do a lot of damage to a car if you hot wire it wrong. You could end up burning the car down.
ALTINATOR OR STARTER. JUMP START CAR, TAKE POSITIVE CABLE OFF BATTERY,IF CAR DIES IT IS ALTERNATOR. GOOD LUCK
You can not get heat from cold water, The engine has to run long enough to get the water in the engine HOT. That is were you get heat from HOT WATER-- Coolent
many things could be wrong......if you are losing antifreeze it could be a hose, water pump, a radiator leak, head gasket....check for any orange or green fuild under the hood of the car and any signs of somthing being wet.......if no fuild is lost could be the themostat...if u have no heat in the car it could be a sign of the themostat...the themostat could be stuck closed...this is if there is not major damage to the car entarnaly to the engine....
You could be burning your coolent. Has your car started to over heat.