is there a 'master' blend door that would explain this?

[bmishoe]

2003 Yukon XL.
Air to the rear is ice-cold, but driver and passenger air are both more tepid. I went through the actuator calibration (set in auto mode, pulled fuse, restarted), and while is was calibrating I felt the front air get ice cold, but when cal was finished, it returned to being more tepid.

I can easily believe that the blend door actuator is bad, but it seems odd to me that both the driver AND the passenger blend door actuators would go bad at the same time. Is there any other blend door that sits ahead of those 2 that would explain this?

Is there a way I can test the 2 blend door actuators individually?

Thanks in advance...

 

[swathdiver]

2003 Yukon XL.
Air to the rear is ice-cold, but driver and passenger air are both more tepid. I went through the actuator calibration (set in auto mode, pulled fuse, restarted), and while is was calibrating I felt the front air get ice cold, but when cal was finished, it returned to being more tepid.

I can easily believe that the blend door actuator is bad, but it seems odd to me that both the driver AND the passenger blend door actuators would go bad at the same time. Is there any other blend door that sits ahead of those 2 that would explain this?

Is there a way I can test the 2 blend door actuators individually?

Thanks in advance...

Yep, get out your Tech-2 or other bi-directional scan tool and test them out. Yes, they can go bad at the same time, or more likely, they've been getting worse incrementally over the last eighteen years. The mode door can also make do this.

 

[S33k3r]

Don't we have 3 blend doors? One on the driver's side, one on the passenger side, and one in the middle (the infamous one that requires dash deconstruction to reach)?

 

[bmishoe]

can anyone comment...so what I did is pull the driver side blend door actuator, since it's relatively easy to get to. I had set the temp to 60 and the actuator was all the way to one of the hash marks, i.e. it appeared correct. More importantly, I manually twisted the blend door shaft to the extreme, and the air up on the driver side was still tepid...so there must be *something* sitting ahead of it.

@swathdiver you mentioned the mode door, can you elaborate?
or can anyone else elaborate on if there's a door that sits ahead of these 2?

bear in mind the rear air is super cold, so I don't think it could be a problem under the hood...

 

[treehan77]

Not sure if rear air gets cold air “first in line” or not, could it just be low on refrigerant?

 

[swathdiver]

can anyone comment...so what I did is pull the driver side blend door actuator, since it's relatively easy to get to. I had set the temp to 60 and the actuator was all the way to one of the hash marks, i.e. it appeared correct. More importantly, I manually twisted the blend door shaft to the extreme, and the air up on the driver side was still tepid...so there must be *something* sitting ahead of it.

@swathdiver you mentioned the mode door, can you elaborate?
or can anyone else elaborate on if there's a door that sits ahead of these 2?

bear in mind the rear air is super cold, so I don't think it could be a problem under the hood...

The mode actuator controls where the air is sent to, windshield, bi-level, up and down, etc. If it is not right, it too can bleed off air. The mode door is accessed from the driver's footwell.

 

[Sparksalot]

I’ll have to admit I’m completely baffled how many actuators there really are and where each is located.

 

[bmishoe]

ok, I can understand what you are describing, but wouldn't the mode be more or less the 'final' door, i.e. it would come after the mix, not before, wouldn't it?

 

[bmishoe]

Let me bring in one more data point. Before today I assumed the blend doors somehow because of the front/rear difference. But let's assume it's not those...is there any portion of "under the hood" hardware that's separate for front vs. rear? Like for instance an orifice tube?

 

[bmishoe]

final thought, just thinking outside the box...do the passenger/driver blend paths ever...cross paths? In other words if the driver blend door was fine, but the passenger one was broken and bleeding off, would any of that hot passenger mix be able to get into the driver side path?

 

[S33k3r]

final thought, just thinking outside the box...do the passenger/driver blend paths ever...cross paths? In other words if the driver blend door was fine, but the passenger one was broken and bleeding off, would any of that hot passenger mix be able to get into the driver side path?

I didn't dig a lot into this as I ended up paying a mechanic to fix it. But the symptoms I suffered were running AC because it gets freaking HOT in Texas, and having the driver's side -- and ONLY the driver's side -- blow heat; everyone else got AC.

But, from the information I have read across multiple GMT800 groups, there are three doors/actuators/whjat-have-you in the front on the GMT800 trucks; one at the driver's footwell, one at the passengers foot well, and one completely behind the dash. The one behind the dash is rated at 9 hours of labor to disassemble the dash, replace the problem part, and reassemble the dash.

As an aside, and this is a wild-ass guess, there are separate units conditioning the air between the front and the rear systems. There is a part, for example, in the right rear wheel well (inside the cab) that has something to do with air going to the back part of these trucks. So I am thinking that bmishoe's problem is something under the hood as opposed to a door issue. But, at this point, taking it to a mechanic and getting it professionally checked would seem the wisest course of action. The trick there being making sure you had a mechanic you can trust.

I don't know where he is located, but if he is in the Dallas/Ft. Worth Area of Texas, I can direct him to an honest mechanic.

 

[Rocket Man]

I didn't dig a lot into this as I ended up paying a mechanic to fix it. But the symptoms I suffered were running AC because it gets freaking HOT in Texas, and having the driver's side -- and ONLY the driver's side -- blow heat; everyone else got AC.

But, from the information I have read across multiple GMT800 groups, there are three doors/actuators/whjat-have-you in the front on the GMT800 trucks; one at the driver's footwell, one at the passengers foot well, and one completely behind the dash. The one behind the dash is rated at 9 hours of labor to disassemble the dash, replace the problem part, and reassemble the dash.

As an aside, and this is a wild-ass guess, there are separate units conditioning the air between the front and the rear systems. There is a part, for example, in the right rear wheel well (inside the cab) that has something to do with air going to the back part of these trucks. So I am thinking that bmishoe's problem is something under the hood as opposed to a door issue. But, at this point, taking it to a mechanic and getting it professionally checked would seem the wisest course of action. The trick there being making sure you had a mechanic you can trust.

I don't know where he is located, but if he is in the Dallas/Ft. Worth Area of Texas, I can direct him to an honest mechanic.

Yes, the front and rear have their own separate systems. The rear is located behind the passenger side rear compartment. There’s a separate heater and ac unit there, with its own blend door and mode door with corresponding actuators. Up front there’s 4 actuators- blend doors for passenger and driver temp control, mode door to tell the air which vent to blow out of, and recirc door to tell the system to either draw outside air in or to recirculate the inside air. The recirc is the hard one on the NBS. I replaced mine in a couple hours by only removing the dash cover and then removing enough screws from the supporting structure that I could pry it up enough to get to it.
So in total that’s 6 actuators.

 

[Sparksalot]

Yes, the front and rear have their own separate systems. The rear is located behind the passenger side rear compartment. There’s a separate heater and ac unit there, with its own blend door and mode door with corresponding actuators. Up front there’s 4 actuators- blend doors for passenger and driver temp control, mode door to tell the air which vent to blow out of, and recirc door to tell the system to either draw outside air in or to recirculate the inside air. The recirc is the hard one on the NBS. I replaced mine in a couple hours by only removing the dash cover and then removing enough screws from the supporting structure that I could pry it up enough to get to it.
So in total that’s 6 actuators.

Are the actuators themselves the same part number, or is each one different?

 

[Rocket Man]

Are the actuators themselves the same part number, or is each one different?

I’m not sure, I think there’s 2 or 3 different ones. It gets confusing.

 

[Sparksalot]

I’m not sure, I think there’s 2 or 3 different ones. It gets confusing.

Figures.

 

[Rocket Man]

Figures.

IIRC Rockauto helps a bit but it’s still stupid.

 

[George B]

These things are hard to diagnose without a bidirectional scan tool.

@915_Tahoe can help with a part number for the actuator.

 

[Sparksalot]

These things are hard to diagnose without a bidirectional scan tool.

@915_Tahoe can help with a part number for the actuator.

I’m having troubles getting t3ch2 to chat with candi. I’m pretty sure one of the actuators is acting up, and was thinking to have a replacement on hand.

 

[George B]

I’m having troubles getting t3ch2 to chat with candi. I’m pretty sure one of the actuators is acting up, and was thinking to have a replacement on hand.

My tech2 does that too. I found its the connector between it and the longer cable. I have to work it together really hard.

 

[Sparksalot]

My tech2 does that too. I found its the connector between it and the longer cable. I have to work it together really hard.

Which one, right connector right at the unit, or the one on the right side of the candi twit in this pic.