Front heater works perfectly but rear heater is just blowing cold

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

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

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!

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.

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?

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.

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.

So this control valve is for rear heat only?