Rear HVAC actuator problem and HVAC1 fuse?

[far eastan]

Rear HVAC Actuator

2006 EXT LT 4.2
I'm currently struggling with the problem of rear HVAC.
This is a matter of popularity. There are many threads.
I read about not only the HVAC issues but also about calibration after replacing the alternator.
Something close to my problem was in the TRAILVOY thread, but it was unsolved.


A similar problem occurred in 2021, and I replaced two rear actuators. For several years, there were no issues.

I replaced the battery this time, but for more than a month, there have been no issues.
But recently there has been a problem.
After the engine starts, the rear blower does not move.
After a minute or a few minutes, you will hear a loud knocking sound from behind.
The knock continues for quite some time.
The rear blower then moves.
Calibration was also performed.
I removed the actuator and checked the inside, but there was no chipped gear.

I have a question: Does the fuse on the HVAC1 have something to do with the rear calibration?
I watched it on YouTube and he had reset the knocking sound of the rear actuator by removing the HVAC1(fuse39).

I have removed the HVAC2(fuse36) and performed the calibration, but will it be effective to remove the HVAC1?

I wish I could give it a try, but I'm hesitant considering the possibility that the front HVAC actuator might break.
If it has something to do with the rear, I'd like to test it out.

I also looked at the image to see the position of the front actuator gear.
Is there an image of the correct position of the gears somewhere on the rear actuator too?


There may be other things to fix.

1. Auxiliary Heater & Air Conditioner Control Assembly
2, MODULE, BLOWER MOTOR CONTROL (AUXILIARY HEATER)
3, or reset by GM dealer.

Thank you very much.

 

[mrrsm]

With a dearth of *Spot On* information available,,, I thought, "I'll have a Lash" and Copy-Pasted your Query into Nomic's *GPT4ALL* and... due to the lengthy Post involved, I chose the Llama 3.1 8 Billion Token LLM (Large Language Model) because *IT* has a very "hungry" 128KB Prompt Entry capacity.

All of what follows took place entirely Off Line and none of this information was leaked, processed in a cloud or released in any other way than via the Screen Prints of the results as you see below in these Two JPEGs.

Bear in mind that the accuracy of the responses from THIS particular LLM has been running fairly high at around 85% to 90% and when compared with what Humans might either provide as ad hoc or "Hit or Miss" replies, as can often be the case, regardless of any Forum visited...That performance is pretty respectable for something only having "Artificial Intelligence".

So take what is listed below in the best sense of the offering and of course... cross check what *IT* had to say with other sources, as no one should ever claim that LLMs can invariably produce perfect responses:

Your Complete First Post...



Nomic's *GPT4ALL* Llama 3.1 LLM Response:



Nomic's *GPT4ALL* can be Freely Downloaded and Installed via their "One Button" easy installation procedures for Windows, MAC and Linux Operating Systems. This AI Chat-Bot requires NO GPU and NO INTERNET Connection for general use and will support a wide array of useful and advanced LLMs:

https://gpt4all.io/index.html?ref=localhost



This is an Example interaction between *GPT4ALL* and a *Human*:





[Mod edit: Deleted references to parts for FRONT actuators]

 

[Mooseman]

@mrrsm , That gear kit you posted is for the front actuators. Deleted references to it.

I haven't had an EXT in a long time and my rear HVAC never worked. I even blocked off the rear A/C lines and only used the front.

When I first got my EXT, it had that clicking noise on startup and would eventually stop. The rear HVAC does the recalibration each time the truck is started, unlike the front or it tried to move the door to the requested position. It is caused by a bad actuator. Even if the gears look intact, it skips inside the part that is attached to the door. I tried to fix it, replacing the actuator. It stopped for a while and it eventually came back. I decided to just disconnect the rear actuators and blocked the rear A/C lines. It was too much trouble to fix and I never had anybody sitting back there.

 

[far eastan]

thank you.
It took a long time to translate the English written on the image.
Sorry for the late gratitude.
The HVAC1 is related to the rear blower control.
If the HVAC1 fuse is removed, there is a possibility that a problem may occur with the front actuator.
I understood these.




In the video, the removal of the HVAC1 was successful in calibrating the rear actuator, but this is a last resort.
And assuming the actuator was broken, I ordered the parts.


Until the parts arrive, I will consider the possibility that the parts may not be broken.


I have now understood the range of motion of the actuator (temperature).
And I could understand which was colder and which was warmer.
It has been found that if the HVAC2 fuse is removed for a certain amount of time, even if the fuse is set up, it will not be able to operate the rear HVAC either from the driver's seat or from the second seat.


If you have calibrated, you can operate from either side.
If the rear blower is not moving, the actuator (temperature) will not move.
The actuator remains in the "cold" position until the air blower begins.
From what I've observed, when the power is turned off, the flap doesn't stay in its final position, but waits in the "cold" position.

Also, even if the HVAC2 fuse is unplugged and the front HVAC temperature control slider is set to "cold" at the bottom, warm air will come out of the front panel.
After installing HVAC2, cold air will come out from the front after calibration.
The air conditioner is not on.


Now, I'll look at the error message again.
Then, put the rear control panel back in the "cold" position before unplugging the fuse.

I'll try and find out a little more what's going on.

Thank you everyone.

 

[far eastan]

The flap No. 36 (GM says Valve, temp) is connected to No. 33.The shaft of the flap has broken.Japan does not have parts.I'm looking for it on ebay.It appears that there are no parts that are made up of the flap alone.GM 89023340 Case AsmIt took more time to fix it.









What determines the range of motion of an actuator?Is it determined by the electronic circuit board of the actuator and the gear?Or is it a computer like an ECU?Is it possible that it could be fixed simply by shifting the gear position?The actuator movement is constant when removed from the flap.I'll do some more research.

 

[Mooseman]

When installed, the system makes the actuator run through the range of motion of the flap door and learns where each end of that range is. Then it knows not to go beyond those points.

Broken shafts have been reported before. Unfortunately, no fix was indicated except one to use JB Weld epoxy to reattach the broken piece of the shaft. And any OEM part numbers reported in those very old threads are likely no longer available.

Rear AC damper is clicking, and I find the shaft is broken

My rear AC actuator was clicking. Usually for only a minute or so after startup, and turning the rear AC on would mostly stop it. FInally I got tired of that so I took it apart today. I got the actuator out with half the shaft. The rest of the shaft is still connected to the door, and I can...

gmtnation.com

Rear HVAC actuator repair - snapped off shaft. What to do now?

Replaced stereo today and disconnected the battery. Damn, I should not have done that because the rear HVAC actuator started clicking again. Husband and I took rear panel apart and got to the actuator. When we took actuator off, post snapped off. Oh crap. We tried to glue it back together with...

gmtnation.com

Rear HVAC repair

2003 Envoy XL SLT w/ auto climate control. Rear blower does not work and clicking noise passenger rear when battery disconnected. Dis-assembled and ran reset after pulling the 30 amp fuse for 10 seconds, blower works but mode door shaft (#37) is broken. Blower works after reset when I turn...

gmtnation.com

 

[far eastan]

I found one, but it was pick up only.
ebay.com/itm/145462215400

My actuator doesn't learn even after calibrating it.
I replaced it for an ACdelco item a few years ago.
It's exactly the same problem.
I bought a new ACdelco part, but within a few years the parts cost doubled.
I'm looking into why the actuator "correctly" remembers the wrong stop position.

 

[Mooseman]

I would be leery of a used housing like that one on eBay from a wrecking yard as they might not have completely checked it for any broken internal parts, like the flap doors. Looking at how it was taken out where they just cut and hacked wires and lines, I would bet that it's not in perfect condition. Shipping is possible but just to Canada, they want $208USD on top of the $120USD cost. I can only imagine the cost to ship to Japan!