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Which Actuator has Overall Control of Temperature?

T

ToaKamate

New Member
Joined
Feb 14, 2022
Messages
5
Greetings all,

You can read a summary of my issue below. In my research, I now know there are actually 3 actuators for this dual-zone digital system. My issue is NOT a floor/dash, passenger/driver, fresh/recirculate/defrost issue - it is a hot/cold issue from all vents. I thought I would try an inexpensive fix of replacing the actuator that controls the main blend door, but not sure if one of the three do that? It seems like it would be the one under the dash on the passenger side - but advice would be appreciated.

2004 Avalanche with automatic climate control. Unless you have encountered this specific problem, it might be impossible to diagnose. When this issue appeared I thought for sure it was the climate control module/panel inside the car. I replaced it twice now - but the problem persists.

Sometimes the blend door actuator doesn't do what it should. In the winter, even after the engine is at temperature - with the heat set at 90 degrees, it is blowing cold air from ALL the vents. Most of the time if I turn the car off and back on several times - it finally kicks in. The opposite happens in summer - sometime it blows warm/hot air from ALL the vents with the temp set to 60. Again, restarting the car 1-4 times finally gets the blend door to do what it should. And, there are times when it works the first time I start the car with no restarting necessary - go figure?

So, the problem isn't the digital control module (unless I got 2 bad replacements with the same exact issue) - so what else could it be that restarting the car one to four times finally gets the main/overall blend door to work? Assuming one of the actuators has overall control of the temperature, it seems like it looses it calibration or something and restarting the car (sometimes several times) finally get it right? Or worn contacts or worn gear in an actuator?

My Foxwell OBD scanner shows no codes - but based on advice in other threads I just ordered a BAFX Bluetooth scanner and will try with the car diagnostics app. But it seems this may be more of a mechanical issue.
 
The blend door actuator is the one you think it is in the passenger side foot wheel.

There are many Youtube videos describing the repair of that and the other actuators.

Mine does as you describe, every great once in a while.

I found a resync will often fix the problem for long periods of time.

Start the engine and then turn everything about the HVAC system to OFF.

Shut down the engine and disconnect the battery for 10-15 minutes.

Reconnect the battery and start the engine.

Cycle everything on the HVAC system to every possible position.

If you have a sunroof, cycle it through all of it's extremes, as well.

This procedure resyncs all of the actuator positions with the computer.

I found if I ever disconnect the battery for some reason without first turning everything on the HVAC system to OFF, then the actuators go wonky after the battery is reconnected.

So, I try to remember to first turn off the HVAC system, then disconnect the battery.

Sometimes, that just isn't possible.
 
Similar issue happened to me a few years ago. Turned out to be something shorting out randomly due to pieces of the cracked dash floating around down there.

2010 ac only blows cold air sometimes

My 2010 LTZ AC is acting up. Sometimes it will blow cold air, sometimes it won't. I got one of those AC Pro things hoping that would fix it. The pressure on the low port was fine so I didn't add any. The compressor runs, but it just blows warm air sometimes. Where/what do I need to check next?
www.chevyavalanchefanclub.com www.chevyavalanchefanclub.com

I don't think the 2004 has the dash crack issue like the later models, so probably not your root cause. But maybe it can provide you some information.
 
Thanks for the replies. I'm hoping it is a calibration issue with the main blend door actuator. Sometimes when I park the car, turn it off and pull the key, I notice the battery drain light stays on. If I don't notice it and turn the key back on and off again - the battery will drain totally dead in a day or so. I'm pretty good about check it but sometimes miss it - as I did a couple months ago.

It's possible that the battery going 100% dead caused the HVAC control unit to loose calibration. I just did the easy type of reset for the control unit (as shown is numerous youtube videos). If that doesn't work then I'll try the major reset Ext4me suggests. If that doesn't work I'll replace the actuator and go from there.
 
For HVAC codes in Car Diagnostic Pro - Choose Scan All Faults under GM Scan Utilities. Choosing Clear All Faults will clear all codes and reset your HVAC so that it re-calibrates. Yes, losing battery power can screw up HVAC.

When you replaced your controls, did you program it for your particular vehicle?

There are right and left side temperature doors with separate actuators on them, so doubtful that both would malfunction together. I think the problem has to be control of them. 90-Degree setting bypasses any temperature regulation or temp sensors, so sensors aren't the problem. Think you are on the right track. Just loss of calibration due to battery being down. I have this problem with my 2004 if I disconnect or run down the battery completely. I do a reset with Car Diagnostic Pro and then all is fine until next time it happens to lose power completely.

IIRC it reports a bunch of HVAC codes until after the reset.
 
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OK, neither calibration reset method worked. Clearing all the codes (there weren't any except some pending ones where tests had not been completed) didn't help. So I just ordered a new actuator for that main blend door. In the meantime I restarted the car numerous times until I finally got it to blow heat and then unplugged the connector for that actuator so it can't go back to cold. A few years back I had a major rodent issue in that car - they had built nests in the blower box, the main fuse distribution box (and chewed through the main harness). For all I know the blend door itself is all gunked up with rodent waste ;)

We'll see if the new actuator helps. If not, I'll 3D print a handle for that blend door to replace the actuator. Had to do that for my 2001 RAM truck 2500 because the actuator went bad and you simply can not find the proper replacement with the correct wiring connector. I live in Colorado, so I usually either need full heat or full A/C. At least the electric windows still work.....
 
Yours has 2 blend door actuators, one for drivers side and one for passenger side. The one on the bottom controls the drivers side temp only, so if both sides are acting up at the same time then your rodents may have caused a problem with one of the temp sensors. I don’t know much about the aftermarket scan tools, but if you know somebody with a Tech2, you can go into the HVAC data list and see what all the sensors are reading, and this might give you an idea of why it’s not correctly adjusting the temp. There are multiple temp sensors that work together, and if one of them is reading wonky than it could be affecting the system. The two blend doors work separately from each other, so it’s not likely that the actuators are malfunctioning at the same time
 
ToaKamate said:
OK, neither calibration reset method worked. Clearing all the codes (there weren't any except some pending ones where tests had not been completed) didn't help. So I just ordered a new actuator for that main blend door. In the meantime I restarted the car numerous times until I finally got it to blow heat and then unplugged the connector for that actuator so it can't go back to cold. A few years back I had a major rodent issue in that car - they had built nests in the blower box, the main fuse distribution box (and chewed through the main harness). For all I know the blend door itself is all gunked up with rodent waste ;)

We'll see if the new actuator helps. If not, I'll 3D print a handle for that blend door to replace the actuator. Had to do that for my 2001 RAM truck 2500 because the actuator went bad and you simply can not find the proper replacement with the correct wiring connector. I live in Colorado, so I usually either need full heat or full A/C. At least the electric windows still work.....
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Did you "Clear all Faults" using Car Diagnostic Pro and the be BAFX OBD2 adapter? This resets the dual zone HVAC in my 2004. You will know when reset when the temp display goes to 75 and the actuators start cycling though their ranges.

There is also a pull fuse method that is the factory published reset method. Its not just a pull it and wait method so you will need to look it up if you want to use it. I did it once amd then found out how to do with the scan tool.

Again, setting to either 90 or 60 bypasses all temp sensors so they are not the problem.
 
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OK, at a total loss here. Per 2004Slickside comments above. Yes, I've used the pull the fuse methods numerous times - and the controls reset to to 74 degrees and then run through all the cycles, etc.

It's not the passenger floorboard blend door actuator after all. I ordered a new one but after my last post (about making sure the old one was set to full heat and then unplugging it - the next time I started the car - same issue. At least I now have an extra actuator.

I always test with the temp set to 90 - which should bypass the temp sensors. The issue of no heat is from all vents and all modes (so it's not the driver or passenger dual control actuators.) If its not a temp sensor because of 90 degree setting - I mean, what the heck?

Here is another weird thing I've noticed. Once I do get the heat to work - then if I make multiple stops after that (meaning parking the car for a little while) - the heat works for the rest of the day. It's the next time (next day, next week) I start it the problem starts again.

Other than the blend doors - is there something else that would completely shut-off the heat from the Cab?
 
Here's the factory info (attached). Tech2 can command the HVAC controller to go to full hot on either blend door. That is the logical thing to do to test. Not sure if my Vident I-link 400 will do that command, but you don't have that one either. I'll look into it out of curiosity.
 

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  • 2004AvyHVACScanToolControls.pdf
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2004Slickside said:
https://www.obdii365.com/upload/pro/...807657729.xlsx

Vident claims to do active testing on 2004 Avalanche HVAC - all the boxes are checked including active tests - but no special funtions mentioned. If you're truly interested in buying one to work on yours, let me know and I will hook it up to my 2004 and see what it can do.
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Hey, thanks for the PDF - that will come in handy. I'll check with a couple of the mechanics in the area and see if they have a tech 2 or Vident. Really don't want to invest in an expensive scanner for this one issue. Bottom line is I really need to get another newer vehicle (but not in the current market :)

I wanted to give the Avalanche to my son who, in his infinite wisdom, bought a rear-wheel drive muscle car with 3" ground clearance - and we live in Colorado.

Thanks again for taking the time to help me on this issue - I do appreciate it. I'll keep this thread updated as I find out more.
 
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