HVAC Control Head?

[drdave81]

Just want to make sure I'm not missing anything here. My HVAC only blows out of the dash vents. When I actuate the mode door with a Tech2, I can get it to sweep from the dash, to the floor, defrost, and back. So I know the actuator works. Seems like the control head would be the issue. I've also done the recalibration procedure, with no change. It always stays on the dash after the Tech2 runs the actuator sweep. Is this a common issue, or am I missing something else?

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

@swathdiver may be able to give you some insight and/or guidance in troubleshooting this issue with the Tech 2.

 

[Doubeleive]

Just want to make sure I'm not missing anything here. My HVAC only blows out of the dash vents. When I actuate the mode door with a Tech2, I can get it to sweep from the dash, to the floor, defrost, and back. So I know the actuator works. Seems like the control head would be the issue. I've also done the recalibration procedure, with no change. It always stays on the dash after the Tech2 runs the actuator sweep. Is this a common issue, or am I missing something else?

if you are not getting any feedback bcm codes from a actuator, then you could try reprogramming the control head or just replace it. the fee is $40 per vin code for 2 years of programming for unlimited programming on that vin. you will need a pc/laptop and a serial port and the cable for the tech2

 

[drdave81]

Sorry, was on vacation for a few days. I'm not getting any DTCs. The fan control and temp both work fine, just the mode knob. Running the actuator via Tech2, it will move, so I know it's not the actuator. Just need to find one in good shape like mine is. Off to a junk yard today, assuming rain holds off.

Doubelieve, you mention reprogramming. Are you referring to a flash update for the control head? I wasn't aware these were flashable. Or am I misunderstanding what you mean.

 

[drdave81]

Another control head in, does the exact same thing. Actuate the mode door with Tech2, and it sweeps between all 3 levels. Stop the actuator and it goes right back to blowing out of the vents regardless of what the controls are set to.

 

[Doubeleive]

where did you get the one you put in it now? if it is used did it come out of the same style truck or did you just get one that looked the same?
depending on the year and style then yes you can put a new calibration on it with the tech2 and using acdelco tds web, they charge $40 for 2 years of unlimited programming per vin number.
have you scanned the hvac system for any dtc's? with the tech2 it should also tell you if the commanded state does not match actual state, being it is a nbs it might not give all the data it does on a nnbs though.
also if you have previously replaced any actuators if you used the wrong one this problem will occur because even if the actuator looks the same and fits the same it won't work the same it will do exactly what is happening now. has it always done this? or is this a problem that just happened since you owned it?

 

[drdave81]

where did you get the one you put in it now? if it is used did it come out of the same style truck or did you just get one that looked the same?
depending on the year and style then yes you can put a new calibration on it with the tech2 and using acdelco tds web, they charge $40 for 2 years of unlimited programming per vin number.
have you scanned the hvac system for any dtc's? with the tech2 it should also tell you if the commanded state does not match actual state, being it is a nbs it might not give all the data it does on a nnbs though.
also if you have previously replaced any actuators if you used the wrong one this problem will occur because even if the actuator looks the same and fits the same it won't work the same it will do exactly what is happening now. has it always done this? or is this a problem that just happened since you owned it?

- The one I got was a used one out of an 02 Yukon, same part number as the old one.
- Earlier, the only code I had was U1500 - Inter Device Dedicated Bus Malfunction. Checking again after playing around with the tool now sets B0248 - Air Flow Control 3 Circuit.
- I haven't replaced any actuators because it works when the tool commands it. I have only owned the vehicle for a week, it was one of the things I noticed when I purchased it. The seller gave me the "hmmm, guess I hadn't noticed that before". Trying the recalibration in the tool and pulling the fuse for 15 seconds, then letting it run for 45 seconds didn't fix the issue either.

Checking the commanded and actual states were pretty close on defrost and floor, within a couple of counts, yet it stayed on vents. When commanded to the vents, the commanded counts went to 0 while actual stayed at 67. This would lead me to think that the actuator is moving, while not moving the mode door, yet when the tool commands it to move, then it actually will push air out of the defrost/floor. That would make me think it works.

I may try a used actuator, since the junk yard has a 1 year warranty on all the parts, so if it doesn't work I can just return it. Try to rule out something else.

 

[Doubeleive]

- The one I got was a used one out of an 02 Yukon, same part number as the old one.
- Earlier, the only code I had was U1500 - Inter Device Dedicated Bus Malfunction. Checking again after playing around with the tool now sets B0248 - Air Flow Control 3 Circuit.
- I haven't replaced any actuators because it works when the tool commands it. I have only owned the vehicle for a week, it was one of the things I noticed when I purchased it. The seller gave me the "hmmm, guess I hadn't noticed that before". Trying the recalibration in the tool and pulling the fuse for 15 seconds, then letting it run for 45 seconds didn't fix the issue either.

Checking the commanded and actual states were pretty close on defrost and floor, within a couple of counts, yet it stayed on vents. When commanded to the vents, the commanded counts went to 0 while actual stayed at 67. This would lead me to think that the actuator is moving, while not moving the mode door, yet when the tool commands it to move, then it actually will push air out of the defrost/floor. That would make me think it works.

I may try a used actuator, since the junk yard has a 1 year warranty on all the parts, so if it doesn't work I can just return it. Try to rule out something else.

That air flow control circuit 3 is your clue, the actuators can go bad it may work when command with the tech2 but then goes back to doing whatever it wants and the tech2 see's it is not working right, it's a smart yet dumb system it can only point you so far.
B0248 Possible Causes · Faulty Mode Actuator
I am willing to bet once you get a working actuator in there then it will be fine.

 

[drdave81]

I'll try that and let you know. Too many threads go without any follow up on a fix. Thanks for the input.

 

[Fjs0001]

I have a similar issue. My blend doors are always stuck on hot. After I replace the fuse to recalibrate, they shift to allow cold air and then move back to hot. I hope you have success, please follow up.

 

[drdave81]

Still working this out, also have a couple other things that sidetracked me. I grabbed two actuators from the junk yard. It's been raining whenever I have time. Hope to get one installed today and give it a try.

 

[drdave81]

Finally got around to doing this. New (used) actuator took care of it. All good now. Air temp takes FOOORREEVERRR to go from hot to cold, but that will be for another day.

 

[malmed]

I am having a very similar problem... 03 Yukon Denali, digital climate control... Hot air blowing out drivers vents when on AC and AC blows passenger side just fine.... I put in a new lower blend door actuator, did the reset procedure, and still the same. Manually move the door and it blows correct... I pulled the new actuator out, to watch it move, plugged into the harness, no movement... disconnected ground for 10 minutes, started truck, no movement on actuator. Tried rest procedure once more, watching actuator, no movement no matter where I set controls... When I try the reset, it does not seem to go thru any 'system test', it sets itself to 74 degrees and auto, but it never changes between floor, vents, defrost, hot, cold, nothing.... just sits. If change to defrost, it goes to defrost, or lower heat if I switch it, but the actuator never moves.

So, now I'm thinking there was never a problem with my original actuator, it was the digital climate control all along?

Anyone have an idea for me to try?

 

[malmed]

Original problem was only hot air blowing out of drivers vents.... I installed a 'new' used digital control unit, recalibrated, and the actuator still does not move... I cannot install it because the slot is in the wrong position... the door it controls only moves about 1/4 turn and the slot in the actuator will not line up with the position of the door.... but, just hanging there, plugged in, it never moves, and it is my second new one, neither moves.... all fuses are good... I don't know what to try next....

 

[Fless]

On an '03, wouldn't the digital control unit need to be programmed with the Tech 2 and TIS2000?

 

[Fjs0001]

Original problem was only hot air blowing out of drivers vents.... I installed a 'new' used digital control unit, recalibrated, and the actuator still does not move... I cannot install it because the slot is in the wrong position... the door it controls only moves about 1/4 turn and the slot in the actuator will not line up with the position of the door.... but, just hanging there, plugged in, it never moves, and it is my second new one, neither moves.... all fuses are good... I don't know what to try next....

The rear AC hot/cold door broke in my 05 Escalade. I grabbed an entire rear unit and three actuators out of an 02 Escalade to use in my 05. The 02 actuators had metal rotating shafts verses the plastic ones in my 05. I assumed they must be built better. None of the 02 actuators worked with my 05. I installed the old 05 actuator and it worked perfectly. Either all three of the 02 actuators were bad or GM changed something over the years. Maybe you have the wrong actuator model?

Or maybe the actuator rotated too far and the gears aren't meshed together inside it anymore. This happened to me once. I took it apart and realigned the gears. I then plugged it back up without mounting it so that I could get it to rotate to the correct position of the door. Once in position, I unplugged it to stop it from rotating. Then I installed the actuator and plug it back up for calibration.

 

[JonnyTahoe]

Finally got around to doing this. New (used) actuator took care of it. All good now. Air temp takes FOOORREEVERRR to go from hot to cold, but that will be for another day.

No problems removing the used ones from the junk yard trucks or installing them in your truck? No problems getting the new one lined up properly? I had all kinds of problems.

 

[malmed]

Either all three of the 02 actuators were bad or GM changed something over the years. Maybe you have the wrong actuator model?

.

I am thinking that may be the problem... I just ordered one from Amazon that said it was the right one for my Yukon.... then when it didn't work, I assumed my bad control unit ruined it, so I bought another one... they very well may have both been the wrong ones. Good call. Now... How do I find the right one? (I threw the original away, I may have a picture of it).

 

[malmed]

Found a pic I took of the original...

 

[mattbta]

The part number in your pic was replaced by 89018365, which is what I replaced my bad original (52402588) with in my 04 with auto climate.