heater doesnt get hot

[jakegday]

hello all. im working with an 81 fairmont, 3.3L 6 cyl. my problem is that my heater does not get hot. it barely gets warm. this is obviously after the engine has completely warmed up. i turn the heater temp all the way up, i turn the fan switch to about 2 or 3, and all i get is barely luke warm air. if i turn the fan to speed 4, the air becomes cool, almost cold.

i have replaced the thermostat and coolant. im sure the water pump is fine....
the only thing i can think of that im gonna try today is getting behind the glove box and making sure that valve on the heater core is opening all the way, other then that i have no ideas. could the heater core just be bad? or is this not a symptom of a bad heater core??

[MagicRat]

Check the blend door.... good idea.

I am not sure about your car, but many cars have a valve in the heater core line which closes off coolant flow to the core unless the heater control is switched on. These valves are usually vacuum operated, so this switch (if it exists) might be stuck or the vacuum line is disconnected or not working.


Also, the core might be clogged inside.

First check: The next time the engine has fully warmed up, feel both heater core lines. They should feel as hot or hotter than the upper radiator hose. If they don't, then coolant flow is impared. If both heater lines are nice and hot, check the blend door.

[jakegday]

Originally Posted by MagicRat

Also, the core might be clogged inside.

First check: The next time the engine has fully warmed up, feel both heater core lines. They should feel as hot or hotter than the upper radiator hose. If they don't, then coolant flow is impared. If both heater lines are nice and hot, check the blend door.

that is a GREAT idea, cant believe i didnt already think of that.
i guess that cable controlled "valve" i was thinking of thats connected to the temperature adjustment lever is actually the blend door. its working.
i will look for the vacuum controlled valve you mentioned, and feel both hoses.

if its not clogged, could the heater core just be bad, due to time? or is that not an option with these?

[Torch]

Heater cores typically don't go bad and still look fine, either they leak or get plugged up, or (for whatever reason) the hot anti-freeze never makes it into the core.

[jakegday]

ok guys. once warmed up, the 2 heater core hoses did not match temperature. one was clearly hotter then the other. i tried "flushing" the heater core, and a BUNCH of brown gunk did shoot out, but my heater still blew cold. so i replaced the heater core. the heater core is now brand new, and both hoses going to and from the core have been inspected for clogs. they are both clean.

but still, even with my brand new heater core, both hoses do not match temperature. the top radiator hose and the thicker heater core hose get hot, but the thinner heater core hose remains cold. and, needless to say, my heater is still blowing cold

any suggestions?

[Torch]

It sounds like you have a valve in there somewhere that is not opening that is not letting the anti-freeze get into the core.