My heater does not work started out the heat wasn't functioning?

KYLEMILHAUPT

MEMBER
2007 CHEVROLET SILVERADO
5.3L
V8
2WD
AUTOMATIC
123,456 MILES

Started out the heat wasn't functioning so well. Engine started to run hot, but wasn't overheating. This all over 2 days turned to warning lights for hot engine/overheating and no hot air from the blower. Still blows cold though. I'm mechanically inclined enough to switch out a pump or heat sensor or thermostat and what not. I just could use sure fire direction in how to better assess the problem. I'm disabled and have a limited income, so if I could replace the one thing that's wrong and not just run on down the line. I have only 1 vehicle too and live in the boonies, help. Any advice to a novice on how to do a flush, without a fully stocked shop? Like with a garden hose.

Thursday, February 13th, 2020 AT 12:18 PM

35 Replies

JACOBANDNICKOLAS

MECHANIC
110,144 POSTS

Hi,

What you described sounds like the coolant level is low. Have you checked it? If it is full, the first thing I would suggest is flush the system and replace the thermostat.

Let me know. As far as a flush, here is a link explaining how it is done:

https://www.2carpros.com/articles/coolant-flush-and-refill-all-cars

THis guide will help us fix the heater operation

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

Please run down these guides and report back.

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Thursday, February 13th, 2020 AT 6:05 PM

KGREENE

MEMBER
3 POSTS
2005 CHEVROLET SILVERADO
5.3L
V8
4WD
AUTOMATIC
130,000 MILES

Driver side blows cold air while passenger side blows hot air when heat is on. I changed the blend door actuator for driver side still blows cold air. I even moved flap for blend door by hand to see if changing the position would make hot air come from driver side vents. But it did not. Still blows cold air I am at a loss for what it could be.

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Friday, April 30th, 2021 AT 2:44 PM (Merged)

KGREENE

MEMBER
3 POSTS

Okay, so I flushed core like you said from both sides small amount of debris cam out but not a lot to plug it. Still the heat only works on passenger side. I turned A/C on and only cold air came from passenger side. Is there some sensor in there that could be bad why it only blows fan air on driver side?

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Friday, April 30th, 2021 AT 2:44 PM (Merged)

ASEMASTER6371

MECHANIC
52,796 POSTS

Nope, no sensor. You said you moved the door manually and no heat. That leaves only the heater core.

Roy

Heater/Vent Module Replacement

Removal Procedure

1. Drain the engine coolant. Refer to Cooling System Draining and Filling See: Cooling System > Removal and Replacement.
2. If equipped remove the auxiliary battery.
3. Reposition the inlet heater hose clamp from the heater core.
4. Remove the inlet heater hose from the heater core.
5. Reposition the outlet heater hose clamp from the heater core.
6. Remove the outlet heater hose from the heater core.
7. Remove the I/P carrier. Refer to Instrument Panel Carrier Replacement See: Dashboard / Instrument Panel > Removal and Replacement.

Image (Click to make bigger)

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Friday, April 30th, 2021 AT 2:44 PM (Merged)

KGREENE

MEMBER
3 POSTS

I changed temperature blend door all set thank you. Now I don't have to freeze!

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Friday, April 30th, 2021 AT 2:44 PM (Merged)

TSCOTT0325

MEMBER
2 POSTS
2004 CHEVROLET SILVERADO
V8
4WD
AUTOMATIC
90,000 MILES

I have changed the thermostat and flushed the system the truck is coming up to temperature okay, still getting very little heat.

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Friday, April 30th, 2021 AT 2:45 PM (Merged)

DOCHAGERTY

MECHANIC
9,603 POSTS

This sounds like you have low engine coolant or the temperature blend door actuator stopped working but to but sure this video and guide can help us fix it.

https://youtu.be/SNRb6pSwYuU

and if the temperature blend door needs replacement here is a guide that can help with diagrams below to show you on your car.

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

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.

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Friday, April 30th, 2021 AT 2:45 PM (Merged)

TSCOTT0325

MEMBER
2 POSTS

Yes, the truck was low on coolant got the heater working again thank you

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Friday, April 30th, 2021 AT 2:45 PM (Merged)

ATJIS

MEMBER
1 POST
2003 CHEVROLET SILVERADO
121,000 MILES

I have the manual temperature control with two sliders. Yesterday I noticed the system was blowing cold air even though I had the sliders all the way up to hot. When I touched the slider and adjusted them down a fraction of an inch, the system immediately started blowing hot air again. This problem continued for about a day where the system would work for a while, then stop blowing heat until I adjusted the selector down a bit, then back up. This morning the selector no longer makes any difference and my system blows only cold air.

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Friday, April 30th, 2021 AT 2:45 PM (Merged)

KHLOW2008

MECHANIC
41,814 POSTS

The slider is for changing the position of the blend doors between heat and cool and it has since stopped working. You would need to check why it has stopped, which could be due to some linkages going bad or out of adjustment.

These guides will help us fix it

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

and

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

Please run down these guides and report back.

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Friday, April 30th, 2021 AT 2:45 PM (Merged)

CARLA REED

MEMBER
27 POSTS
2003 CHEVROLET SILVERADO
V8
TURBO
2WD
158,000 MILES

After warming up heat blows hot air, approximately fifteen minutes later it blows cool air, then approximately fifteen minutes later it'll blow hot air again. It continues to do this. What could be the problem?
Thanks

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Friday, April 30th, 2021 AT 2:46 PM (Merged)

SCGRANTURISMO

MECHANIC
4,897 POSTS

Hello,

This could be problem with your blend door actuator. I have included a couple of links down below.

https://www.2carpros.com/articles/car-heater-not-working
https://www.2carpros.com/articles/replace-blend-door-motor

Please go through these guides and get back to us with what you find out.

Thanks,
Alex
2CarPros

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Friday, April 30th, 2021 AT 2:46 PM (Merged)

CARLA REED

MEMBER
27 POSTS

Will do. Thanks so much.

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Friday, April 30th, 2021 AT 2:46 PM (Merged)

CARLA REED

MEMBER
27 POSTS

Just wanted to say thanks for your quick response/advice. It was the thermostat and I found out the hard way that my thermostat/housing is all one piece. But it is fixed.

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Friday, April 30th, 2021 AT 2:46 PM (Merged)

DARRELL HAYWORTH

MEMBER
1 POST
2000 CHEVROLET SILVERADO
V8
4WD
AUTOMATIC

Have replaced thermostat checked fuses still no heat?

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Friday, April 30th, 2021 AT 2:47 PM (Merged)

BILL BURT

MEMBER
1 POST
2000 CHEVROLET SILVERADO
3.8L
V8
2WD
AUTOMATIC
255,000 MILES

Only one hose going from the engine to heater core gets burning hot to touch, the other only gets warm. It never runs hot always goes on the gauge where it supposed to. I put anti freeze in it still no luck. I am at a loss. What do you recommend for me to do?

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Friday, April 30th, 2021 AT 2:47 PM (Merged)

ASEMASTER6371

MECHANIC
52,796 POSTS

Good evening,

It sounds like the heater core is clogged. I would remove both hoses from the heater core on the firewall. Then use a garden hose and run it through the core. Run it both ways several times until the water is clear and has an even flow from running it both ways.

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

Roy

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Friday, April 30th, 2021 AT 2:47 PM (Merged)

CTT

MEMBER
1 POST
2000 CHEVROLET SILVERADO
173,000 MILES

I am wanting to know where the actuator that adjust where the heater air output is located.

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Friday, April 30th, 2021 AT 2:47 PM (Merged)

FIXITMR

MECHANIC
9,990 POSTS

Drivers side of HVAC case under dash. Check out the diagrams (Below). Please let us know what you find.

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Friday, April 30th, 2021 AT 2:47 PM (Merged)

47BOBBER

MEMBER
3 POSTS
2000 CHEVROLET SILVERADO

I bought the truck this past spring and with the days getting colder noticed that my heat does not work as it should. Coolant level is fine, the hoses get hot. The truck has very little heat when idling but gives off more as you are driving around. Even full blast while driving around, it never gets warm enough to the point where I would want to take my coat off. I doubt it would even melt away ice. I saw someone else on this site have a similar problem and they said they "flushed" out their heater core and it seemed to work fine after that. Is that a feasible solution or is there something else going on here?

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Friday, April 30th, 2021 AT 2:48 PM (Merged)