Heater not working, blows cold air why?

Tiny
AFLIEGEL
  • MEMBER
  • 2005 BUICK LESABRE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 44,125 MILES
When I set Automatic on my Heather/Air Conditioner control I am not getting heat coming out of the vents. There was a noise being made in the off position which went away when I pushed the automatic button that is not there now. A fluttering noise of some kind.
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Monday, November 1st, 2010 AT 12:15 PM

53 Replies

Tiny
HMAC300
  • EXPERT
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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Wednesday, November 3rd, 2010 AT 6:15 PM
Tiny
HOAGY106
  • MEMBER
Thanks. I had to get a new bleed door actuator works great now.
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Monday, March 22nd, 2021 AT 12:51 PM
Tiny
SAMRUSHING
  • MEMBER
  • 2004 BUICK LESABRE
The a/c works fine but when you cut the heater on it won't blow anything but cold air. I've checked all the hoses and the lines. What else could I look at?
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Monday, March 22nd, 2021 AT 12:51 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
It sounds like the heater core is plugged. If you remove both hoses, see if you can get water to flush through it using your garden hose. Spray it into both hoses so you backflush too.

Let me know if that helps. NOTE: If you can't get water to go through, it will most likely need replaced.

Joe
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Monday, March 22nd, 2021 AT 12:51 PM (Merged)
Tiny
PATTY S
  • MEMBER
  • 2004 BUICK LESABRE
  • 3.8L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 130,000 MILES
No heat. Over the last couple weeks, my mechanic:

- Replaced the blend-door
- Replaced the thermostat
- Burped the system, twice

There is minimal heat while idling. When driving, about 1/2 mile down the road, it starts blowing cold air.
The blower works. The climate controls switch from defrost to heater, blend, and vents. It blows cold air out of all of them.
Mechanic noticed the coolant was down quite a bit in a weeks time.

I live in rural Wisconsin. I nearly froze going to an appt Friday. Please help me! My mechanic said he needs to ponder over this for a few days.
I was researching on line. The problem most closely resembles a problem with the heater control valve. However, my mechanic says my car doesn t have one.
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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good evening,

When he had the blend door off, did he verify the door was actually moving back and forth?

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

Are both heater hoses hot to the touch with the engine at normal operating temperature.

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

He is correct, there is no heater control valve in your engine.

I would also, remove one of the hoses while running to see if there is flow to and from the core to be sure there is circulation.

Roy

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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
PATTY S
  • MEMBER
Thank you, Roy. After he replaced the blend door, it seemed to work, but then we had that record breaking week of 75 degree temperatures, so hard to say for sure. My mechanic is usually quite thorough.
I will have to wait until Monday to ask him those questions. He said he needs to clear his head this weekend. He wants to ponder over it until Monday. He is not used to being stumped.
What really has us stumped is that the heater blows medium warm air when idling.
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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Yep, sounds like a circulation issue.

Roy
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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
PATTY S
  • MEMBER
What would cause that?
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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
The hoses may have debris inside causing the coolant to be restricted and no flow the proper amount of coolant. He needs to check all the way back to the intake manifold.

Roy
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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi,

I hope you don't mind me jumping in. Roy is correct saying it is likely a circulation issue. Here is an easy way to check:

Start the vehicle and turn the heat on high. Allow the engine to run until it reaches operating temp. Then you can turn the engine off. Open the hood and feel both heater core hoses. Both should be hot (one may be slightly warmer simply because it is a supply line). If one is cool and one hot, there is a circulation issue.

The heater hoses are behind the engine and attach to the heater core. They are rubber hoses approximately 1" in diameter. See attached pic.

Also, let us know if the engine is reaching operating temperature.

Here are the bleeding directions. There is a bleeder on the thermostat housing. I'm not sure if that is what you are using.

_______________________
1. Fill the radiator and the coolant reservoir to the full cold line with GM Goodwrench DEX-COOL (R) or Havoline DEX-COOL (R). To ensure sufficient engine cooling, freezing and corrosion protection, maintain the protection level at -37 C (-34 F) lower.
2. Wait for two minutes and recheck the level of the coolant in the radiator. If necessary, add coolant to radiator until the coolant level is at the base of the radiator fill neck.
3. Install the radiator pressure cap, making sure the arrows on the cap line up with the coolant recovery tube.
4. Place the heater and A/C control in any A/C mode except Max and the temperature in the highest setting.
5. Start the engine and allow to idle until the louver radiator to coolant pump hose is hot.
6. Cycle the engine speed up to about 3000 RPM and back to idle five times. Slowly open the bleed valve on the top of the thermostat housing for approximately 15 seconds to expel any trapped air in the cooling system.
7. Close the air bleed valve. Do not overtighten.
8. Allow the engine to cool to outside temperature. Ensure the coolant level in the reservoir and the radiator are at the proper levels.
_____________________________

Let us know what you find or if you have other questions.

Take care,
Joe
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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
PATTY S
  • MEMBER
I flushed the heater core I think that did it, thank you so much I have heat again!
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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
PATTY S
  • MEMBER
I guess I thought the system flush would have cleared the hoses.
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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
You are welcome.

Always glad to help.

Roy
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Monday, March 22nd, 2021 AT 12:53 PM (Merged)
Tiny
BUFFY45
  • MEMBER
  • 2004 BUICK LESABRE
  • 175,000 MILES
Hi! For the past few days I've noticed that after my car has warmed up and is blowing warm air, it will all of a sudden start blowing cold air. This will usually happen after driving the car for about 15-20 minutes.
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Monday, March 22nd, 2021 AT 12:54 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
First, make sure the coolant is full. If it is, check this for me. With the engine warm and the heater on high, check to see if both heater core hoses are hot. Do this when it is blowing cold air and let me know what you find.
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Monday, March 22nd, 2021 AT 12:54 PM (Merged)
Tiny
SHARBUT
  • MEMBER
  • 2001 BUICK LESABRE
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 185,000 MILES
I have a 2001 Buick LeSabre-Custom, v-6, 3800 series engine. My heater isn't working. It blows cold air. Engine thermostat has been changed. Upper radiator hose is hot after being driven. Any ideas on what the failure might be?
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Monday, March 22nd, 2021 AT 12:54 PM (Merged)
Tiny
ERNEST CLARK
  • EXPERT
Your upper radiator hose is supposed to be hot, and so is the bottom. When the thermostat was changed, did they bleed the system of air? Because this can be your issue if air is trapped in the heater core.

If that's good, then your issue is either a stuck control shut off valve, blocked heater core, Stuck/broke blend door inside the HVAC unit or a leaking vacuum line/solenoid in the HVAC unit.
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Monday, March 22nd, 2021 AT 12:54 PM (Merged)
Tiny
SHARBUT
  • MEMBER
How would I determine the "stuck control shut off valve"? And where is the shut off valve?
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Monday, March 22nd, 2021 AT 12:54 PM (Merged)
Tiny
ERNEST CLARK
  • EXPERT
The shut off valve is located on one of the small diameter coolant hoses that enter and exit the firewall on the passenger side. It's a small metal valve with a linkage hooked to it. Once your engine warms up, have someone turn on the heater controls (high) and watch the movement of the valve.
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Monday, March 22nd, 2021 AT 12:54 PM (Merged)

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