My heater is not working?

Do you have heat in any mode? Have you checked the coolant level? This guide can help us fix it

https://www.2carpros.com/articles/car-heater-not-working

Let us know what happens and please upload pictures or videos of the problem.

Nice work this guide can help others then

https://www.2carpros.com/articles/replace-blend-door-motor

please use 2CarPros anytime we are here to help.

How old is your thermostat? Sometimes flushing can trigger a t-stat to stick.

It can be intermittant.

I need to clarify your situation however. Are there 2 problems?

Is the volume, or force of air through the vents (regardless of temp) not always working or only on particular speeds?

Is the temperature not raising enough and blowing cold air a separate problem?

Or are both a conern like I think you wrote? :
And you very welcome :wink:

I don't know if the problems are related or not. I'll give my thoughts and maybe we can get through this.

Since there isn't a difference in volume whe the settings are changed, I question if there is a cabin air filter that is plugged (may not have one) or if there is a blend door in the heater ductwork not operating. Sometime a faulty heater control unit in the dash will not instruct the door to open or it can be machanically stuck.

As far as the heat. Since you're getting no heat at all, I wonder if there is coolant circulating into the heater core. That is a part that is like a radiator only its in your firewall area behind the glove compartment. The blower motor fan blows over this and you feel the volume and heat when it works right. Since the temp gauge drops when the blower is on, it makes me think the fan is cooling the coolant and therefore it is circulating.

Lets do this.
First run the truck until it's to temperature. Raise the hood and find two heater hoses that go into the firewall toward the passenger compartment. Should be on the passenger side. Feel how hot they are. They should be very hot going in and just slightly cooler coming out.
Sceondly, Call the Dealer and ask for a cabin air filter for your truck, you may need the VIN #. If they say there isn't one, we eliminated that. If they show one, replace it.

I just got finished replacing the heater core in my 2001 Blazer. I will list what mine did, and allow you to draw your own conclusion.

My heat basically stopped being warm during the summer months when it was not being used that much. Therefore I was not aware if the loss of heat was gradual or all at once.
I flushed my radiator system and got the worst looking black soot water from it. I tried to flush my heater core but it was clogged. After working the pressure on the intake and exhaust sides back and forth, the water began to flow. After about an hour of flushing the fluid flowing thru my heater core was clear again, and the heat worked great. I discovered that the inner lining of both heater hoses had dissolved and contaminated my system. I replaced the hoses and thought I had a great fix.
About 2 weeks later the heater core began to leak. I was now faced with a $1,000 shop visit, or replace the heater core myself. Make no mistake, changing this core is a heack of a job, and I would recommend knowing maintenace before attempting it.
Everything is working in fine order now, and I am not sure if any of my problems are related to yours. I did not have reduced air flow with my situation other than the normal flow reduction of routing the air across the heater core.

My advice on trouble shooting is to disconnect the heater hoses at the firewall, and after placing a water deflector over your distributor, flush the heater core. DO NOT overpressurize the core. Just a normal flush pressure to make sure the core is flowing.
If you have never changed your thermostat, change it. It is very cheap and easy to do. I find it alot easier on this model to refill your engine block thru the thermostat hole prior to installing it. It takes less to bleed the system and just makes the job quicker.
Now, if the heater core and thermostat are not your problem, then there are tests on the body compter that can be run to determine if you have a control problem. I am affraid that might have to be done by a certified shop.
Good luck and hope you get heat before the winter is over.
Mike

Your welcome.

Did you bleed the air out of the system?

Based on the other posts, the heater core would be good to backflush. Seems like an inherent problem with these.

I remember when I was trouble shooting my heating problem and there were several sensors and systems that are controlled by the body computer that would have direct control on the temperature of the heat. All of them required a scanner tool to accomplish, so that might be a way to go. I would however do the heater core flush and see if that helps.

Chances are the thermostat is stuck open which would cause the problem. That is the first thing I would replace to see if it helps.

Let me know what you find.
Joe

I looked at your question. i found this diagram in "prodemand" i researched a chevy pickup k1500 automatic with a manual hvac- if this is wrong, let me know, i look for another diagram. i noticed there are other doors and valves in the diagram, i don't know how they are actuated. This guide can help as well

https://www.2carpros.com/articles/car-heater-not-working

Check out the diagrams (Below). Let us know what happens and please upload pictures or videos of the problem.