92 heater problem

my 92 skylark has no heat!, ive changed the thermostat, temp sending unit, flushed and cleaned the radiator, still cant get any heat in the car and were about to face winter in iowa. one thing that strikes me as odd is when i accelerate and the heater is on, my airflow will switch to the vents until i let off the gas then it returns to the floor?????? is the unit under the dash bad?

First you want to confirm that the Hoses going to the heater core are actually getting coolant... you could have a blockage or, more likley, an air pocket in there preventing coolant flow. Run the car for a bit so the coolant heats up to normal temps.. then feel the hoses to see if they are warm... if they both are warm then your problem is elsewhere, but if only 1 or neither are warm, then it's not flowing any coolant.


Don't worry about the airflow just yet.. I would check to make sure the Temp. selector is working though(the air "blend" door could be stuck to fresh air)... see if it regulates the temp from cold to warm with the AC on.

Airflow problem could be a couple of things:

1: Bad selector switch
2: Bad Vacum diaphram (actually open/closed the air door)
3: Broken air door
4: Vacum leak preventing operation of the air door.

I'm betting that since it moves freely that its a bad Vac Diaphram... I can't rember for sure, but I believe that's the only thing that puts resistance on the door... so if the door is just free swinging, then the door is either broken or the Diaphram is bad. See if you can move the door cable by hand, and if the airflow changes with it.

I'm sure I'm forgetting some things, but best I can do from memory right now.

Good Luck.

i checked the heater core lines inside the car (under the dash) one is warm with the car running and one is cold, also the heater core itself does not heat up.

as far as the airflow from what i can tell all the blend doors are working properly they seem to be doing what they are supposed to based on the selection its on, and the door that opens to allow heat to come in is also functioning.

i checked the heater core lines inside the car (under the dash) one is warm with the car running and one is cold, also the heater core itself does not heat up.

as far as the airflow from what i can tell all the blend doors are working properly they seem to be doing what they are supposed to based on the selection its on, and the door that opens to allow heat to come in is also functioning.

Ok.. You're not getting any circulation through the Heater Core. I'm not sure on 90's+ cars, but some cars have a valve in one heater hose that is vacum operated and shuts off flow when the AC is on (helps the AC cool better)... that valve is known for sticking shut. Look and see if you have a valve in the line that has a Vac. hose running out of it.


If not, or it's OK.. then loosen a clamp on the engine side of the Cold hose(make sure you break the hose loose so it'll leak).. see if you can get coolant to leak out of it.. You might have to run the car (be very careful). Once you get coolant out of it, tighten it up and test to see if your heater works. I've had 3 cars in the past where I've done coolant changes and had air trapped in the line causing your problem... I allways loosen a heater hose when filling up my Radiator (from empty or really low) now, and haven't had a problem since.

If that don't work, then you have other issues.. most likley a blocked heater core. Easy way to test is to cut off a garden hose, and put it on one end to see if any water comes out the other. It sounds like the Heater core is easy to get to on your model, so that's a plus if it's bad.

I'd try bleeding the system first though.. most likley you've got a air pocket in there.

just want to update, this problem turned out to be a bad heater core, rather completely plugged with junk, the previous owners apparently kept fillin it with leak stopper rather than fix the leak, so i just slapped a new one in rather than tryin to flush out the old one (and if you tore that far into the dash to get to the heater core ya just as well replace it because its a pain to get in there) heat works great now, still getting the weird air circulation when accelerating, but for an iowa winter i dont care where its coming out of it as long as its hot :)

how did u replace the heater core exactly??