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So due to circumstances beyond my control, my garage baby is about to become a daily driver. My heater blows cold, and I need to fix it ASAP! Could it be the heater core?
 

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If it's not leaking and temp gauge reads normal, then a cheap guess is disconnect both heater hoses from engine. You need to flush out h/core. With one heater hose hanging down, put garden hose up to other hose and flush out with water. Then switch hoses and flush the other direction. Reconnect to engine, refill radiator and warm up and see if you get heat. If it works, a cheap fix.
 

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What year car? it may have a heater control valve that stuck closed not allowing water to circulate similar to the plugged heater core idea above.

Any pics of the hose area going into the firewall? that's where the control valve would be located. Are the hoses hooked up? Many time PO's disconnect them due to leaking heater core.

Is the blower working? moving air out the vents?
Jon
 

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Could be something as simple as your thermostat is stuck in the open position. If so, the coolant will not reach operating temp and you won't get any warm air from your heater. Should only cost you about $8.00 for a new thermostat and $1.00 for a new thermostat gasket.

You can check to see if your thermostat is any good by boiling it in a pot of water.
 

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Could also be that the heater door isn't adjusted correctly; the control wire outer shield could have come loose. Look under the dash and watch the door control when you move it up and down.
 

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Could also be that the heater door isn't adjusted correctly; the control wire outer shield could have come loose. Look under the dash and watch the door control when you move it up and down.
I agree--are your heater controls working smoothly?? It's probably the flapper door in your heater box stuck if all mentioned above checks out. The heater controls and the box would be the first place i would look also. PS-- Probably be the easiest thing to start with.
 

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Warm it up and feel both heater hoses. Both should be hot enough to be uncomfortable to keep your hand on them although one maybe slighter hotter than the other. If both are hot you have good water circulation thru the heater core circuit. Then I would check, as recommended previously,the flapper door.
Is upper radiator hose getting hot ? If not then you have a thermostat problem
 
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