Yet another no heat/ac thread.... I know, I know.

[Diesel6point6]

Ok guys, I know you've seen this a million times but trust me I've researched the hell out of this and I've hit a wall.

03 Yukon Denali. I had the typical no temp change on the driver's side, in my case the AC worked fine but heat did not. Ok for the time being but it's about to get cold in CO so I need to get this figured out. So off to the forums I went and I saw thread after thread of this and the general consensus was the blend door actuator on the passenger side. Easy enough. Replaced that and it still didn't operate, it just cranks itself to the cold side just like the OEM one did and gets stuck there. After recalibration (pulling fuse, on/off, jump on one foot, spin 3, not 4, 3 times, yada yada) I still experienced the same symptoms but now the air will only blow on floor mode....great now I've got two actuators bad!! So yesterday I do this process a few more times along with some profanity and eventually I get everything to work as it should. Both temperature and mode are operating, such a relief! Nah, that'd be too easy!! I get in this morning and it's back to blowing cold on the driver's side again. WTF!! And not to mention the back doesn't have heat either but I haven't even dug into that yet but after this experience I'm sure looking forward to it.

Any thoughts on what could be going on? I've verified the blend door functions as it should. I know the core is working because when I manually turn the blend door it works as it should (both hot and AC work on both sides) and both hoses get super hot. Coolant level is topped off. One thing I find VERY interesting is in every recalibration video/write-up I see it says after pulling the fuse the digital screen will default to 74, well mine defaults to 75 so I'm not sure what's going on there.

So idk if my system is just cursed or what but my head is spinning. Any ideas would be greatly appreciated. I just bought the vehicle a few weeks ago so I'm blind as far as what has been worked on or not.

 

[OR VietVet]

The A/C heater control switch panel may be needed. If you look at RA there are 4 options there. You might want to also do this for future reference info for the rig:


We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

 

[Diesel6point6]

The A/C heater control switch panel may be needed. If you look at RA there are 4 options there. You might want to also do this for future reference info for the rig:


We recommend that you put all your rig(s) info in your signature so we all don’t have to guess at year, make, model, engine size, trans, rear axle locker…….etc. While you may have posted pertinent info in your first post, you may forget to do it again and the info is needed by us anyway. Makes it way easier on all members that attempt to help, to have that info right up front. It is also recommended that you take a pic of your RPO codes, on the inside cover of the glove box, and post that image in your signature. All this info will greatly help those that will try to help with a problem.


If there is any other info, like upgrades, mods or recent mechanical/maintenance work done, that would be helpful in any post as well. Too many times a question is asked by the poster and after about 10 responses we find out that the poster has done recent work to attempt to fix the problem or work that was done that SEEMS not related to the problem.

Thank you. I will look into the switch panel. I've been curious if that's what is bad and causing all these headaches. Any way to test it to be sure? I hate just throwing money at something. I'm hitting the junk yard this weekend, maybe they'll have some there.

Also, thank you for the heads up on the signature. I've updated mine with as much info as I can. Like I said, I've only owned it for a few weeks so it's all the info I have unfortunately. Will upload RPO codes as well when I am at the vehicle. I'm driving the Dmax today.

 

[swathdiver]

Ok guys, I know you've seen this a million times but trust me I've researched the hell out of this and I've hit a wall.

03 Yukon Denali. I had the typical no temp change on the driver's side, in my case the AC worked fine but heat did not. Ok for the time being but it's about to get cold in CO so I need to get this figured out. So off to the forums I went and I saw thread after thread of this and the general consensus was the blend door actuator on the passenger side. Easy enough. Replaced that and it still didn't operate, it just cranks itself to the cold side just like the OEM one did and gets stuck there. After recalibration (pulling fuse, on/off, jump on one foot, spin 3, not 4, 3 times, yada yada) I still experienced the same symptoms but now the air will only blow on floor mode....great now I've got two actuators bad!! So yesterday I do this process a few more times along with some profanity and eventually I get everything to work as it should. Both temperature and mode are operating, such a relief! Nah, that'd be too easy!! I get in this morning and it's back to blowing cold on the driver's side again. WTF!! And not to mention the back doesn't have heat either but I haven't even dug into that yet but after this experience I'm sure looking forward to it.

Any thoughts on what could be going on? I've verified the blend door functions as it should. I know the core is working because when I manually turn the blend door it works as it should (both hot and AC work on both sides) and both hoses get super hot. Coolant level is topped off. One thing I find VERY interesting is in every recalibration video/write-up I see it says after pulling the fuse the digital screen will default to 74, well mine defaults to 75 so I'm not sure what's going on there.

So idk if my system is just cursed or what but my head is spinning. Any ideas would be greatly appreciated. I just bought the vehicle a few weeks ago so I'm blind as far as what has been worked on or not.

There are four actuators up front, where is the one you replaced for the driver's side temperature control and what is its part number? I put in the wrong one once and it worked backwards. What year is the Duramax?

 

[Diesel6point6]

There are four actuators up front, where is the one you replaced for the driver's side temperature control and what is its part number? I put in the wrong one once and it worked backwards. What year is the Duramax?

I replaced the one under the kick panel on the passenger side. I verified that's where my issue lies by manually flipping the blend door by hand. Whenever I did that, the air temp did what I wanted it to do (either hot or cold depending on which way I flip it). I pray I never have to change the one in the dash lol. I changed it out with part # 89018365. I hope that's the right one? I was shocked at how many different ones there were but I just matched the part # on the original but am a little nervous the previous owner may have changed it out with the wrong one, hopefully that isn't the case. I also took the old one apart and cleaned it up and mechanically it looked good but you never know when there's electronics involved too. However the new one is doing the same as the old so I suspect the old one may not be bad.

Duramax is an 01 Lb7. It's my pride and joy.

 

[S33k3r]

We had to replace the one behind my dash. Fortunately I could afford to, at the time, have someone else do it. On the flipside, my light sensor was broken, so I got to get that replaced, too... You see, the light sensor replacement also requires the removal of the dash...

 

[OR VietVet]

Thank you. I will look into the switch panel. I've been curious if that's what is bad and causing all these headaches. Any way to test it to be sure? I hate just throwing money at something. I'm hitting the junk yard this weekend, maybe they'll have some there.

Also, thank you for the heads up on the signature. I've updated mine with as much info as I can. Like I said, I've only owned it for a few weeks so it's all the info I have unfortunately. Will upload RPO codes as well when I am at the vehicle. I'm driving the Dmax today.

You can post the Duramax info as well, if you want to. Not all RPO codes need to be posted. Just the main ones like engine, gears, limited slip, transmission and any codes related to the specific question at the next time you have questions.

 

[Diesel6point6]

We had to replace the one behind my dash. Fortunately I could afford to, at the time, have someone else do it. On the flipside, my light sensor was broken, so I got to get that replaced, too... You see, the light sensor replacement also requires the removal of the dash...

Haha, of course all these rather common failing parts are behind the dash! At least you see the bright side with your light sensor (pun intended lol). I remember my ambient light sensor needed replaced in the Duramax, which like your situation, required removal of the dash. I decided to take the shortcut and go through where the radio goes. I've got small hands so luckily I was able to get the old one out ok, but the new one was a different story. One fell down into the depths of the dash, the second attempt I just fed the wire plug through the hole and just kinda wedged the sensor in from the top so it wouldn't move. My dash mat covers it enough to where it's not noticable.

One thing I've learned with these older vehicles is when you start taking apart plastic dash pieces, a clip or two is bound to break and it just never goes back in the way it was so I try and avoid doing that as much as possible. My passenger side door panel is forever like this because I've had to remove it so many times.

You can post the Duramax info as well, if you want to. Not all RPO codes need to be posted. Just the main ones like engine, gears, limited slip, transmission and any codes related to the specific question at the next time you have questions.

Don't have to offer that twice, I'm quite proud of the truck so I'll gladly post the Duramax info haha! With that said, sig updated. I'm on mobile so I tried to format it as best I could, will button it up when I'm on PC.

Makes complete sense to have a detailed sig. Thank you again!

 

[JonnyTahoe]

You will know when your system is cursed when your rear blower motor control module decides to turn on your blower with everything off and you not even in the truck.

 

[Diesel6point6]

You will know when your system is cursed when your rear blower motor control module decides to turn on your blower with everything off and you not even in the truck.

Haha that would be a bit unnerving!

Ok guys I think I may be on to something with the digital control module. Out of curiosity I had my girlfriend pull the module and send me a photo of the back. Sure enough as I suspected it's a Dorman product #599-211, not OEM so at some point in this vehicles life that was replaced. After learning this I'm 99% confident that module is faulty, especially since it's not OEM. The local junkyard has a ton of these for $75 so I'll probably pick one up so long as it's the original and not another knockoff like this one.

I'll report back once I get one.