2001 Chevrolet Blazer no heater

Tiny
LIL0NE
  • MEMBER
  • 2001 CHEVROLET TRUCK
I have a 2001 Chevrolet Blazer with approximately 90,000 mi. Randomly I will lose the heater functionality. For about the last month I could turn the nob to RED (hot) and turn the fan to the highest number 4 and I would at least have some gnerally warm air but not a strong or hot stream of air. I can change where the air flows (eg floor, vents, defrost) and feel that the air is going to the right duct. The last three days I have turned the heater to HOT and the fan on the highest speed and I have cold air (temperature of outside) blowing through my vents that is not very strong at all. When I leave it on the highest fan speed with the hot temperature, I will never receive anything remotely warm but my temperature guage on my dash dropped from 210 (the normal running temp) to 150 in the matter of 5 minutes. My radiator was just flushed two days before this reoccuring problem started back up again. Any suggestions as to dropping temperatures, low blowing power and no heat? Thx sooo much in advance!
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Wednesday, December 27th, 2006 AT 6:27 PM

11 Replies

Tiny
SERVICE WRITER
  • EXPERT
How old is your thermostat? Sometimes flushing can trigger a t-stat to stick.
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Wednesday, December 27th, 2006 AT 7:14 PM
Tiny
LIL0NE
  • MEMBER
I have never replaced it since I owned the car. It's a 2001 and I bought it Jan 2004. Before the flush it was losing the blowing power and heat randomly though not as often. It would happen two days straight then fine for a few weeks than happen a few days again and go back to being fine. This time. Unfortunately the hot air fairies aren't returning the next morning to fix everything for me. Could the thermastat have been sticking randomly before and now it's just completely stuck? I thought once a thermastat stuck it was stuck for good. Thank you so much.
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Thursday, December 28th, 2006 AT 7:58 PM
Tiny
SERVICE WRITER
  • EXPERT
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:
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Thursday, December 28th, 2006 AT 8:40 PM
Tiny
LIL0NE
  • MEMBER
Yes. The force of air out the vents (regardless of where the temperature is turned towards) is weak. I can see a difference from low blow to high but it is not very significant at all. Low is the normal low but each step up above from low hardly increases the force of the air at all.

Aditionally there is the problem where I have absolutely no hot air (it's not even slightly warm air) The air that comes out of the vents is the same on the cold setting as it is on the highest setting.

Strangely, I have noticed however, if I put the blower on highest power and have it on the hottest setting. Even though I am getting the coldest air imaginable blowing out, my temperature guage on my dash will consistantly drop from the normal 210 to 150. This started for the last 3 days. Not sure if it signifies anything at all though.

You are correct, both issues are the concern. I think I would prefer some form of heat (even if there is hardly any power behind it though) over anything. Mornings just barely over single digit temperatures I worry may turn me into a snow angel. Happy New Year and thanks again for all the support; you don't know how much appreciated it is.
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Saturday, December 30th, 2006 AT 5:59 PM
Tiny
SERVICE WRITER
  • EXPERT
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.
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Saturday, December 30th, 2006 AT 9:39 PM
Tiny
MIKEYBDMAN
  • MEMBER
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
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Monday, January 1st, 2007 AT 3:30 PM
Tiny
WSHIREY
  • MEMBER
I had the same problem with my '99 Blazer 4.3L. The iron block causes the heater core to plug completely. Take the heater core hoses off at the firewall-wear safetyglasses before the next step, flush the core out with a garden hose until the water runs clear instead of rusty, take the heater hoses on the engine loose and flush back through them, also remove a radiator hose and flush it as best as you can. You have to be extremely careful when doing this-as to not rupture the core or radiator, but I also used my air line to flush with, you should probably cut the pressure down a bit on your air compressor regulator to be safe when doing this. Put everything back together, get some radiator flush in a bottle-drive it for a bit to bring everything up to temp, your heat should work now. Repeat the flush, don't forget the anti-freeze this time.
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Monday, January 1st, 2007 AT 7:27 PM
Tiny
LIL0NE
  • MEMBER
Installed a new thermastat, figured it couldn't hurt to just replace when I was taking out the old to check. The new thermastat allows me to have only luke warm air on the highest heat setting. It is an immense difference from the ice cold air. But it is really just barely warm at all. I can feel a difference from cold to medium to the hottest setting though.

So my thermastat may have been part of the problem but there's something else down the line that just isn't right.

In regards to the two hoses going into the passenger side of the firewall. One is very hot and the other is just an average hotness. From all the support you have given me this sounds like how it should function.

With the thermastat replaced, turning the blower on highest setting does not cause my temperature guage on my dash to drop any longer.

With the holiday I haven't been able to check on the other air filter but I haven't found anything mentioned about it existing in any of the 2001 chevy blazer manuals I've looked through.

Ive read posts on the heater core. But with my two lines running hot. Would that suggest the circulation is fine and there is no plug?

I'm not sure what else to check next.

Thank you to everyone for all your support and guidance. It's truly amazing!
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Monday, January 1st, 2007 AT 7:49 PM
Tiny
SERVICE WRITER
  • EXPERT
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.
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Monday, January 1st, 2007 AT 8:21 PM
Tiny
MIKEYBDMAN
  • MEMBER
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.
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Monday, January 1st, 2007 AT 8:37 PM
Tiny
LIL0NE
  • MEMBER
I think I'll try the flush. Oddly though. I had perfectly functioning heat for about an hour duration today. Everything was magically back to normal, the blower power was slightly lower than normal but it was almost perfect and the heat was actually hot. Then instantly while driving it was back to just average heat and has stayed that way. Would this signify anything?

Everyone's suggestions are much appreciated and I'm getting in the right direction to having a normal heater before winter ends. Thank you all!
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Tuesday, January 2nd, 2007 AT 6:35 PM

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