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Heater not working please help me fix it?

Tiny
DKVOGEL
  • MEMBER
  • 1999 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 242,000 MILES
Heater not working. Replaced the thermostat heat still not working.
Sunday, December 5th, 2010 AT 11:21 PM

26 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 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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Sunday, December 5th, 2010 AT 11:38 PM
Tiny
CNJHART
  • MEMBER
  • 1 POST
  • 1997 CHEVROLET SILVERADO
I replaced my t-stat and fan clutch and I still have no heat what should I do?
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,833 POSTS
Hey,

You check the heater hoses up by the fire wall with the engine warm. Check your coolant level engine cold. To me though it sounds like you have a temperature blend door actuator that is out which is common. Here is a guide to help us fix your truck which is one of my favorites vehicles btw.

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

and

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

Check out the diagram (Below)

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

Cheers, Ken
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
BALI DEE
  • MEMBER
  • 2 POSTS
  • 1996 CHEVROLET SILVERADO
  • V8
  • 2WD
  • AUTOMATIC
  • 154,000 MILES
Ac works fine, but heater won't blow warm.25 amp fuse is not blown, inside cab?
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
With the engine at full operating temp, locate the 2 heater hoses where they go into the firewall and feel them to see if they are both hot to the touch. If they are.

The temperature is controlled by the use of an air mix door that is operated by an electric motor/actuator. This door can be jammed or the actuator can be inoperative or have stripped plastic gears internally.
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
BALI DEE
  • MEMBER
  • 2 POSTS
Thank you Wrench tech for the timely response. I checked the 2 hoses as you indicated, and it was recognized that one, the outlet of the motor, was indeed as hot as the coolant, but I never was able to get the return hose to rise to the equal temp? I suppose that there's a switch valve that is not working or whenever the hose blew, and was changed before I bought the truck, has possibly clogged the core?(I did have to change the thermostat due to improper reading, and found parts of the old hose fitting logged in the thermostat.) I could find it possible that maybe some of the same metal crumbs could have made it downstream to foul the switch valve?
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
Yes, that would indicate a clogged core. I would remove both hose and flush it thoroughly with a garden hose under pressure from both directions and see if that helps.
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
ANGIE105
  • MEMBER
  • 2 POSTS
  • 1995 CHEVROLET SILVERADO
  • 4.2L
  • V6
  • 4WD
  • MANUAL
  • 150,000 MILES
My husband put a heater in, it will not heat up but the heater is working. Replaced thermostat truck is full of antifreeze. No leaks. Was wondering what would cause this.
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Heater? Do you mean a heater core? Heater motor?

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

Did he bleed the system of all air?

https://www.2carpros.com/articles/engine-cooling-system

Roy
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
ANGIE105
  • MEMBER
  • 2 POSTS
He put in a new heater. He did not bleed it.
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, he needs to bleed it first.

Have him run the engine at 1,200 rpm, remove the cap on the surge tank and add as needed. Keep the heater on until you get heat.

Again, did he replace the heater core or the blower motor?

Roy
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
MARISSA BAER
  • MEMBER
  • 1 POST
  • 1995 CHEVROLET SILVERADO
  • 4WD
  • AUTOMATIC
  • 195,000 MILES
The heating is not working. We had changed both the heating core also put a 204 thermostat in thinking that was the problem. But had no luck with that. What could be the problem?
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,833 POSTS
It sounds like you have a temperature blend door actuator that is not working.

Here is a guide to give you an idea of what you are in for when doing the job:

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

Here is a guide that will give you more options:

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

Below is what it will be like for your car.

Please let us know what you find. I am interested to see what it is.

Cheers, Ken
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
KRAKER
  • MEMBER
  • 1 POST
  • 1992 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
I have a 1992 silverado k1500 305. I have no heat. Replaced water pump, thermostat, and rad, flushed heater core 4 times still no heat. Help!
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 42,833 POSTS
Hello,

It sounds like you have a blend door actuator that is not working. Here are two guides that will help you see whats going on.

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

and

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

Check out the diagrams (Below)

Please let us know if you need anything else to get the problem fixed.

Cheers, Ken
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
CHUCKTODD
  • MEMBER
  • 1 POST
  • 1989 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
I have changed thermostat and flushed heater core. When motor is hot the heater box is hot but no hot air blows in. Fans blow fine but just room temp air. Any suggestions would be helpful.
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
One of your actuators isn't working right, check the ones in pic with the double arrow as one will be temperature.
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
RAPAULSON
  • MEMBER
  • 1 POST
  • 1989 CHEVROLET SILVERADO
  • V8
  • 4WD
  • AUTOMATIC
  • 260,000 MILES
I have checked as the truck warms up, one hose first warms up then the other as the water goes through the core. The blend door operates to change from defrost, windshield, to the floor, heater, but with no heat. Is the blend door also the directional door? How to fix and gain access, even if I can get the door (baffle) to open manually to let the air to blow into the heater core, if that is the problem?
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
WRENCHTECH
  • MECHANIC
  • 20,757 POSTS
The blend door and the mode door are 2 entirely different components.

If both hoses are hot to the touch, then you likely have a blend door problem.

You should be able to access it by removing the glove box.

https://www.2carpros.com/images/external/57432979.jpg.gif
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)
Tiny
BLACKZ71
  • MEMBER
  • 2 POSTS
  • 1988 CHEVROLET SILVERADO
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 275,000 MILES
I have replaced the radiator heater core thermostat and temperature blend door actuator and water pump in the past year. I have no heat and cannot figure out why. Could it be the climate control box? I do not think it is because the display works and I can hear it moving the doors back and forth when I press the button. I cannot think of another part in the heating system! Any help would be much appreciated! Also a few weeks ago the heat was so hot it would run you out, then all of a sudden it just stopped working.
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Tuesday, June 8th, 2021 AT 10:36 AM (Merged)

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