Front heater works perfectly but rear heater is just blowing cold

Tiny
PETE23
  • MEMBER
  • 2005 CHEVROLET TAHOE
  • 12,000 MILES
Front heater works perfectly but rear heater is just blowing cold air out.
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Saturday, January 7th, 2012 AT 10:09 PM

26 Replies

Tiny
HMAC300
  • MECHANIC
  • 48,606 POSTS
It sounds like one of your actuators may not be operating properly.it could either be one in the front heater unit or rear. rear pic enclosed. the right rear quarter trim panel must be removed for access to this.

This guide can help us fix it

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

Check out the diagrams (Below). Please let us know what happens.
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Monday, June 29th, 2020 AT 7:12 PM
Tiny
GD73
  • MEMBER
  • 2 POSTS
  • 2005 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 70,000 MILES
I own a 2005 Chevy Tahoe with the automatic climate control. The rear heater sometimes blows cold air even when the front heat is hot and the vehicle will be up to operating temp. Sometimes it will blow hot air but for the most part it's cold. What would be the causes of this problem. Any help would be great! Thanks
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
Check the rear actuator and see if its moving when you control the rear temp
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
GD73
  • MEMBER
  • 2 POSTS
Where is the actuator located? Is that on the passenger side rear interior quarter panel Thanks for getting back to me.
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
RHALL77
  • MECHANIC
  • 3,361 POSTS
Its on the passengers side of the rear area. Check out the images (Below). Please let us know what happens.
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
JJARRARD
  • MEMBER
  • 1 POST
  • 2004 CHEVROLET TAHOE
  • V8
  • 2WD
  • AUTOMATIC
  • 84,000 MILES
We have heat coming out of the front but no heat blowing in the rear. Air and water is flowing in the rear but no hot air. I'm assuming it's an electrical component that's causing the issue. Any idea what? No problem codes on the dash unit. My first time trying this program. Let's see if it works.

Thanks!
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
BMRFIXIT
  • MECHANIC
  • 19,053 POSTS
SUSPECT BLEND DOOR ACTUATOR(mode actuator) and or control module

this is a picture for the front one rear is at the same idea


https://www.2carpros.com/forum/automotive_pictures/99387_2_17.jpg


let me know if need more info
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
BMRFIXIT
  • MECHANIC
  • 19,053 POSTS
To get to it and check
Remove the rear seat.
Remove the Third Pillar trim panel.
Remove the garnish molding.
Remove the door sill plate.
Remove the quarter panel trim screws.
Remove the quarter panel trim from the vehicle.
Lift the quarter panel to release the quarter panel from the vehicle.


https://www.2carpros.com/forum/automotive_pictures/99387_2_18.jpg

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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
PAR3EAGL
  • MEMBER
  • 7 POSTS
  • 2004 CHEVROLET TAHOE
  • V8
  • 4WD
  • AUTOMATIC
  • 100,000 MILES
Can anybody provide instructions on how to replace the rear passenger area's temperature regulator? The heater works perfectly in the front part of the cab. Everything in back of the driver blows cold air. The A/C works perfectly. I have been told that I have a bad "Temperature Regulator"? Anybody with experience with this? I understand it is located in the trunk area of the SUV. The dealership wants 2 1/2 hours time to fix the problem plus $189 for the part. Thank you for any assistance if you have performed this type of repair in the past.
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
BMRFIXIT
  • MECHANIC
  • 19,053 POSTS
Remove the right rear quarter trim panel.((( Trim Panel Replacement - Rear Quarter - Right (Utility)
Removal Procedure
Remove the rear seat..
Remove the Third Pillar trim panel.
Remove the garnish molding.

Remove the door sill plate.
Remove the quarter panel trim screws.
Remove the quarter panel trim from the vehicle.
Lift the quarter panel to release the quarter panel from the vehicle.))).
Disconnect the electrical connector from the auxiliary air temperature actuator.
Remove the retaining screws from the auxiliary air temperature actuator.
.
Remove the auxiliary air temperature actuator (1) from the rear auxiliary HVAC module
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
PAR3EAGL
  • MEMBER
  • 7 POSTS
Thank you for your answer. It looks like a lot of work, but not very technical. Would you agree? Also, where is the best location to find the exact GM Replacement part at the best price? I am looking for a "Auxiliary Air Temperature Actuator" correct?
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
BMRFIXIT
  • MECHANIC
  • 19,053 POSTS
Dorman product
Check with your local part store supply if they carry it
Check and make sure both heater hoses hot before taking it apart
And if so actuator is to suspect
Not a technical job at all and can be done with patience
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
PAR3EAGL
  • MEMBER
  • 7 POSTS
BMRFIXIT you answerd my question 3 weeks ago regarding the Temp Actuator on a GMC Yukon Denali SUV replacement. WHen you refer to the quarterpanel, you are referrin to the internal trim and not the actual car quarter panel on the exterior correct. I am not finding the screws for the 3rd pillar to remove the interior plastic trim. Do you have any pictures you could email or send to me? Thanks. Glenn
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Friday, February 19th, 2021 AT 7:59 PM (Merged)
Tiny
TALHOE
  • MEMBER
  • 1 POST
  • 2003 CHEVROLET TAHOE
  • 5.3L
  • V8
  • 4WD
  • AUTOMATIC
  • 116,000 MILES
Hi,

I was prepared to purchase and replace the old Control module part number 21997590 with new control module 15832319. I took it apart to check out what I was getting myself into. I seen the temp actuator is in the over travel position. I then noticed the controller had already been replaced and part number 15832319 is already in. So for fun I removed the HVAC 60AMP and 10AMP fuses and then removed the temp actuator. The shaft between the actuator and flapper valve inside the box (not sure what this is called) is actually snapped/broken. I bought the vehicle used last week and not sure how this happened. I looked around online and cannot find how to fix this or what part I need to purchase. I did not go any further and start trying to open the HVAC box. Thanks.
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Friday, February 19th, 2021 AT 8:00 PM (Merged)
Tiny
KASEKENNY
  • MECHANIC
  • 18,907 POSTS
If the arm that connects the actuator and the door is broken then you need to replace the door itself.

I am attaching the process below on how to do this. This is actually inside the housing so you are going to have to remove it and open it up.

Here is a video that covers a bit of this but does not cover this specific issue. However, the info is good and will help understand what is happening.

https://youtu.be/SNRb6pSwYuU

take a look at the attached info and we can go from there.

Thanks
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Friday, February 19th, 2021 AT 8:00 PM (Merged)
Tiny
KENDELLCHADWATTS
  • MEMBER
  • 4 POSTS
  • 1999 CHEVROLET TAHOE
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 160,000 MILES
Rear air only no heat. I have removed rear panel but found no actuator. Every diagram I found doesn’t look like mine. My blower motor is mounted horizontally.
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Friday, February 19th, 2021 AT 8:00 PM (Merged)
Tiny
STEVE W.
  • MECHANIC
  • 12,869 POSTS
Has anything been done to the cooling system or did it get low on coolant? A common reason for the heat in the rear units to stop is an air bubble in the core. The next is a failure in the heater control valve or it's actuator. Those two control the flow of hot water to the rear heater core. Testing the valve is simple. Pull the vacuum hose off the top and apply a vacuum from a hand vacuum pump. If you cannot obtain a vacuum the diaphragm in the valve has likely failed. If you apply vacuum and the heat starts to work the valve is likely okay and the failure is in the control solenoid under the hood or the vacuum lines to or from it.
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Friday, February 19th, 2021 AT 8:00 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Okay, this has a separate heater control valve at the front firewall. I attached a picture for you of the location.

Roy
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Friday, February 19th, 2021 AT 8:00 PM (Merged)
Tiny
KENDELLCHADWATTS
  • MEMBER
  • 4 POSTS
So this control valve is for rear heat only?
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Friday, February 19th, 2021 AT 8:00 PM (Merged)
Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Correct. It controls the auxiliary heat.

Roy
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Friday, February 19th, 2021 AT 8:00 PM (Merged)

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