02Yukon2500
TYF Newbie
I'm having issues with the mode door on my 2002 Yukon XL SLT. I have the auto climate control (the version with the three knobs, not the later one with the LED display in the center). Every since I got the truck a few months back, I've had intermittent issues with the AC. A new blend door actuator fixed one issue, and I was just left with a mode door actuator problem.
While driving, sometimes it would just start toggling back and forth between the two extremes of this actuator (defrost and front vents). But other times, it would just stay on the main vents. Changing settings on the control didn't do anything - it always did whatever it seemed to want to at the time.
I figured the actuator was bad (when I could get it to move, the pot feedback was about 0.8V - didn't change much based on position), but this gave me the excuse to go ahead and buy one of the Tech2 clones off fleabay. Using that, I verified that the counts weren't changing like they should. Using the Tech2, I could now make the actuator move, but the counts didn't reflect the full-scale like they should (it basically stayed at one end of the scale). So, I decided that the actuator was bad, and ordered a replacement.
I installed the replacement, and tested - still not working right. I've forced it to recalibrate multiple times with no change in functions (it moves the actuator during the recalibration, so I'm assuming it's doing it right but I don't know what/how to check more). I'll also note that while I had the original actuator out, I manually moved the two levers and didn't feel any binding, etc. so I don't think there are any mechanical issues. So, here's the current status:
1. When I turn the key on, the actuator goes to the defrost position, no matter what the controller is set to. Changing settings on the controller does nothing.
2. When I read the DTC codes, I get B0248 (Air Flow Control 3 Circuit) and B3761 (Air Flow Control 3 Feedback Circuit). Interestingly, when I read the codes, the actuator always moves to the other end of the range (main vents).
3. If I clear the DTC codes, I immediately get a B0248 again. I don't think it's moved or tried to do anything - it just throws the code again.
4. If I go into the special functions on the Tech2, I can see that all the inputs of the control are working properly - fan, mode, temp, A/C on, auto, etc.
5. The min and max settings never have a value when I look through all the values on the Tech2. It's like it's just never learning them... Side note: And because mine is an 2002 (or just a limitation with my Tech2 clone), I can't force a relearn through the Tech2 (that I've found). I can on my 06 Sierra with the later auto climate control, so I'm guessing it's just a limitation of the early version...
6. If I force the actuator using the Tech2, it looks like it's working fine. When I command "ON", it goes to defrost (commanded position is 255 and actual position is around 247). When I command "OFF", it goes to main vents (commanded position is 0 and actual position is about 10).
7. Interestingly, when I command "ON" and wait a couple minutes, the commanded state goes to "none" and the commanded position changes to 0 and the actual to about 10 counts. Not sure if this is normal or not...
8. I verified all the voltages at the actuator when I was moving it using the Tech2, and they appear correct. Command voltage is normally 2.5V when it's sitting still. Goes to 0V and the actuator moves one way, 5V and it goes the other way. Pot voltage goes between 0V and 5V depending on position...
Based on all this info, I think the actuator is now working correctly, but I'm assuming I still have a problem with the controller (not sure why it would work correctly from the Tech2, but not by itself?)... I ordered a good used one off fleabay to try (after trying a Dorman in my Sierra a while back, I'll never make that mistake again) and I figured I'd see if some of the experts here may have some more insight while I wait for that part to come... With the way that GM has all the control distributed, I'm worried that the problem might be more than what I'd call the controller (the part with the three knobs that you use to change settings). Any assistance is appreciated.
Also, I know that there's a few threads active for AC issues right now, but I figured it was best to start my own vs jumping onto theirs as I don't have anything to add to their specific problems (their issues are completely different than mine, or for a different year vehicle). So, if you're curious why I started another thread, that's why...
Thanks,
Danny
While driving, sometimes it would just start toggling back and forth between the two extremes of this actuator (defrost and front vents). But other times, it would just stay on the main vents. Changing settings on the control didn't do anything - it always did whatever it seemed to want to at the time.
I figured the actuator was bad (when I could get it to move, the pot feedback was about 0.8V - didn't change much based on position), but this gave me the excuse to go ahead and buy one of the Tech2 clones off fleabay. Using that, I verified that the counts weren't changing like they should. Using the Tech2, I could now make the actuator move, but the counts didn't reflect the full-scale like they should (it basically stayed at one end of the scale). So, I decided that the actuator was bad, and ordered a replacement.
I installed the replacement, and tested - still not working right. I've forced it to recalibrate multiple times with no change in functions (it moves the actuator during the recalibration, so I'm assuming it's doing it right but I don't know what/how to check more). I'll also note that while I had the original actuator out, I manually moved the two levers and didn't feel any binding, etc. so I don't think there are any mechanical issues. So, here's the current status:
1. When I turn the key on, the actuator goes to the defrost position, no matter what the controller is set to. Changing settings on the controller does nothing.
2. When I read the DTC codes, I get B0248 (Air Flow Control 3 Circuit) and B3761 (Air Flow Control 3 Feedback Circuit). Interestingly, when I read the codes, the actuator always moves to the other end of the range (main vents).
3. If I clear the DTC codes, I immediately get a B0248 again. I don't think it's moved or tried to do anything - it just throws the code again.
4. If I go into the special functions on the Tech2, I can see that all the inputs of the control are working properly - fan, mode, temp, A/C on, auto, etc.
5. The min and max settings never have a value when I look through all the values on the Tech2. It's like it's just never learning them... Side note: And because mine is an 2002 (or just a limitation with my Tech2 clone), I can't force a relearn through the Tech2 (that I've found). I can on my 06 Sierra with the later auto climate control, so I'm guessing it's just a limitation of the early version...
6. If I force the actuator using the Tech2, it looks like it's working fine. When I command "ON", it goes to defrost (commanded position is 255 and actual position is around 247). When I command "OFF", it goes to main vents (commanded position is 0 and actual position is about 10).
7. Interestingly, when I command "ON" and wait a couple minutes, the commanded state goes to "none" and the commanded position changes to 0 and the actual to about 10 counts. Not sure if this is normal or not...
8. I verified all the voltages at the actuator when I was moving it using the Tech2, and they appear correct. Command voltage is normally 2.5V when it's sitting still. Goes to 0V and the actuator moves one way, 5V and it goes the other way. Pot voltage goes between 0V and 5V depending on position...
Based on all this info, I think the actuator is now working correctly, but I'm assuming I still have a problem with the controller (not sure why it would work correctly from the Tech2, but not by itself?)... I ordered a good used one off fleabay to try (after trying a Dorman in my Sierra a while back, I'll never make that mistake again) and I figured I'd see if some of the experts here may have some more insight while I wait for that part to come... With the way that GM has all the control distributed, I'm worried that the problem might be more than what I'd call the controller (the part with the three knobs that you use to change settings). Any assistance is appreciated.
Also, I know that there's a few threads active for AC issues right now, but I figured it was best to start my own vs jumping onto theirs as I don't have anything to add to their specific problems (their issues are completely different than mine, or for a different year vehicle). So, if you're curious why I started another thread, that's why...
Thanks,
Danny
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