Front heater works perfectly but rear heater is just blowing cold

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.

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

check the rear actuator and see if its moving when you control the rear temp

Where is the actuator located? Is that on the passenger side rear interior quarter panel Thanks for getting back to me.

its on the passengers side of the rear area. Check out the images (Below). Please let us know what happens.

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!

SUSPECT BLEND DOOR ACTUATOR(mode actuator) and or control module this is a picture for the front one rear is at the same idea

let me know if need more info

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.

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.

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

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?

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

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

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,

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

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.

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.

Okay, this has a separate heater control valve at the front firewall. I attached a picture for you of the location.

Roy

So this control valve is for rear heat only?

Correct. It controls the auxiliary heat.

Roy

Heater problem
1998 Chevy Tahoe V8 Two Wheel Drive Automatic

My wife has a 1998 Chevy Tahoe LS. The vehicle is very sound and I have had to make few repairs on it outside of regular servicing. The problem is the front heater blows hot but the rear blows cold as if the a/c was on. It doesn't have dual climate controls just the fan switch for the rear. Both the front and rear blow cold when the a/c is on. I am at my wits end. Can you help???

The heat in that vehicle is controlled by a blend door that regulates heated air flow. it is operated by an electric motor/actuator. The problem can be that the actuator is stripped or inoperative or the door itself could be damaged. This is what needs to be determined by examining the actuator and see if it is responding to heat change commands or not.

The air conditioner works fine in the front and rear, but the heat only works in the front cold air comes out of the rear vents what could be the problem?

try pulling fuse in picture for sixty seconds with key on, then reinstall. it may reset actuator in other picture otherwise that may be the problem and not opening door so it will heat.

2004 Yukon Aux Blower Motor Stuck on "High"

This has the digital auto A/C controls. There is no display whatsoever on the rear HVAC control unit, and the only way I can keep it off is by pulling the 40 amp rear HVAC fuse from under the hood. Is this just a bad control unit or do I need to dig a little further? The display worked when I first turned the rear heat on, but then it went out after I pulled the fuse.

Hi,

If the fan is staying on high all the time regardless of speed selection, chances are the control module itself is bad. Since the lights don't turn on any longer, that is my first suspect.

If you take a look at the attachments below, they provide the diagnostic for an auxiliary blower motor that always runs. See if you feel comfortable performing the procedure.

Here is a link you may find helpful:

https://www.2carpros.com/articles/how-to-check-wiring

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

Take care,

Joe

See pics attached.