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?