my heater stopped blowing hot air

Asked by Jan 13, 2013 at 01:53 PM about the 1996 Chevrolet Blazer LS 2-Door 4WD

Question type: General

16 Answers


The cabin heater in your vehicle produces heat from a heater core. The heater core is a small radiator, located under the dashboard of the vehicle and consists of conductive aluminium or brass tubing with cooling fins to increase surface area. Hot coolant passing through the heater core gives off heat before returning to the engine cooling circuit. The fan for the vehicle's ventilation system forces air through the heater core to transfer heat from the coolant to the cabin air, which is directed into the vehicle through the vents. If there is a lack of hot coolant running through the heater core or less common, a pocket of air trapped in your heater core, the vents will not produce hot air. It is crucial that you immediately check the level of the antifreeze in your radiator and fill it until it is full. Then monitor it and check for leaks. Running an engine without coolant can lead to expensive or irreversible engine failures like head gasket failure and engine damage.

41 people found this helpful.

Can't argue with that joef, an excellent explanation, But there is more, assuming you took his advice and your coolant/antifreeze level is up. The valve that controls the flow of hot water (coolant) in to the heater core could be stuck closed, or the linkage to it broken/ faulty. not letting the water in to the core. Give me a few and I will locate that valve on your car..and what it looks like so you can take a look on your car.

103 people found this helpful.

I went to 4 websites and they all agree,,,something I did not know: Your vehicle does not have one. If you are not getting heat and the engine IS reaching operating temp then check the heater core by touching both heater hoses; they should both be hot. If one is hot and the other is cooler, then the core is plugged up. Try this: disconnect the hoses and take two 3 foot lenghts of clear plastic tubing( to see progress) and attach one to each of the core ends. Now pour a container of radiator flush into both sides and let it sit in the core for ten minutes. After it has set, apply pressure with a garden hose to one side and then the other; that should dislodge the plug; if this does not work, then your core will need replacing. I hope this helps you.

31 people found this helpful.

Excellent answers Joe and David. Solution # 3 is that the core is hot but the air coming out is cool. There is a door that lets cool air bypass the core. Shut the door and air is forced through the heater. That door is controlled by your temperature selector. Some are operated by electric motors. I'll put up a basic GM HVAC diagram - hopes it helps.

34 people found this helpful.

Ok so i am having the same issues, i just replaced the thermostat with one that fails open rather than closed, you said if one hose is hot and one is cold its plugged? what about this door how do i access it im not car savy i just take things apart and figure out how to put them back together but this one is stumping me, the hoses look good, no leaks and the fluid levels are spot on, also the compressor i think its called ( the top rotating thing for ac at the driver side top location of the belt) is spinnning and ac works, so chances are its a plug then?

16 people found this helpful.

auto zone said that there is a blend door,if this is sticking heat will not pass.

16 people found this helpful.

ok,, my doors for my air is y my air conditioner doesn't work. However, i was able last year to get heat, but now, i can't. over the summer, there was this thing that was spinning for the air, but my air doesn't work. Now its cold out and my vents are blowing out cold air. In the summer there was heat coming from the bottom. now nothing. help!!!!

21 people found this helpful.

pls help,,,,,what type of shop would i go to to get this fixed.

3 people found this helpful.

i have a similar problem, but when i parked this morning, i saw steam/smoke coming from the hood, i couldnt pinpoint the exact spot but it was coming from the rear passenger side

5 people found this helpful.

does anyone know the solution for this?

2 people found this helpful.

ok to the solutions I have read, no one said what is really the simplest way to tell if your heater core has gone bad, is if the interior of your windshield gets steamy. also you may have a wet area on the passenger side flooring.

6 people found this helpful.

I have a question. I have a 2003 Yukon. If my front heat blows cold air, is it possible that my back heat will blow hot air? This being the weekend and it starting getting below freezing as of yesterday( when I found out my heat doesn't work right).I wont be able to take it to the shop till Monday.

5 people found this helpful.

Yes ur yukon can blow cold in front while back blows hot. Look for your actuator it's usually behind the glove box just to the left or on the upper right side of the box. Turn your temp back and forth. Your checking to see if your actuator moves. Try placing your hand on it to feel it move or listen closely to hear it move. If it don't move then that's your problem. Replace or for quick temp fix u can unhook it and turn all the components by hand and hook back up. It's not difficult at all to do.

2 people found this helpful.

so i got a 2004 chevy blazer and the heater and defrost will no longer blow hot air but the ac dose work. this was not an issue yesterday. please help. also the enine temp is normal. i should be getting heat! yarrrr helpmee

34 people found this helpful.

Have any of you had a bad battery or replaced a battery and than had this issue with your heater? Think back now, LOL! If so this is a cheap, easy, quick fix that solved the same problem you're all describing. actuator-recalibration-procedure.html and here is a short video to help you along. I did not have the fuse described in the video so I disconnected the battery.

44 people found this helpful.

i have a 99 chevy blazer and my problem is my heat blows hot then cold for a couple of sec and back again not really sure what to do to fix it

25 people found this helpful.

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