Calibration of HVAC issue on 2002 Subruban

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ID Status Date Year Make Model Transmission Type A/C Controls Public/Private
#15483 Closed 2002 Chevy Suburban 1500 public

My mechanics replaced the starter in my vehicle on Monday morning. They had the battery disconnected for awhile and when I went to pick up the vehicle early afternoon there was barely any air movement coming from the vents and no cold air. They realized they needed to calibrate the auto HVAC system. It is now Thursday and they can’t figure out why it’s not calibrating. I know they have tried a bunch of things but not sure what various sequences they are doing. They did find that the 2 ground wires in the relay box on the passenger side of the engine that control the HVAC were severed and were going to replace the relay box. I got a message last night that they are still fighting with it. Both they and myself are very frustrated! I need my vehicle back. I’m not a mechanic but am wondering if they are missing something in the steps. When they plug in the sensor it says the the modes are working but only when it is plugged in. They have also tried a new actuator. Again, I am not a mechanic but all my research has shown there are certain things that should/should not be done. The last time I was there when they were showing me things, they had the door open while working on it. One forum I read said the door should be closed. I also wonder if they are moving the control knobs while it is trying to calibrate – another forum said not to do that. I just need my car back. Can you help?
Sparky

First things first. If you have manual a/c controls on your 2002 Suburban there are no recalibration procedures for the HVAC system.

The following is the procedure if you have auto HVAC controls.

Actuator Recalibration

The HVAC control module will relearn the actuator limits whenever power is disconnected and re-connected to the module.

Use the following steps to perform the calibration update:

    1. Turn OFF the ignition.
    2. Remove the battery positive voltage circuit fuse (Radio fuse in underhood fuse box) of the HVAC Control Module.

Important:  The scan tool must be disconnected from the vehicle to properly perform the calibration procedure. If a scan tool is connected before this procedure is completed, then new calibration values will not be stored.

Important:  Failure to wait 60 seconds will not allow the HVAC control module sufficient time to clear the old calibration values.

  1. Wait 60 seconds.
  2. Install the fuse.
  3. Start the engine and allow it to run for at least one full minute. Do Not Touch anything.
  4. Turn the ignition off for at least ten seconds but no more than 30 seconds.
  5. Restart the engine and check the HVAC operation.

They did this and it didn’t work. It’s an auto HVAC.

Sparky

Chances are then you have one or more faulty actuators but they/someone will need to use a scan tool and diagnostic trees to find the problem.

They have used the Tech 2 scan tool and say the actuators are okay. They can get the various modes to work with the scan tool plugged in but not once they remove the scan tool. They have checked the ground wires as well. They got a new HVAC module but for some reason can’t get the calibration to work.
Sparky

There are a lot of variables in your statements from a technical perspective.

If connecting to the system with a Tech 2 allows the control panel to work then there is likely a voltage issue to the control panel and most likely on the ground side. The powers and grounds must be checked loaded (headlight bulb) and not with just a test light or a multimeter.  Definitely do not rely on an ohms reading.

If the actuators work with the scan tool but not with the control panel the likely issue would be the control panel or some data pid is missing that is preventing the control panel from working properly.

Do you know if there are any codes stored in the HVAC system?

Can you better describe the overall problem?

Does the blower not respond to control changes?

Does most of the air flow come out of the defrost?

Does the air move out of the commanded locations and the blower sounds right but the air flow is weak?

Or something else?
Sparky

Your mechanic is more than welcome to come on this forum and I will discuss ideas here. I don’t do phone consultations unless I have a longstanding rapport with a shop or mechanic for a multitude of reasons.

I feel for your situation and short of helping your mechanic on this forum my best recommendation is for you to ask them to use their scan tool to get the actuators to the most desired locations for summer cooling and disconnect each actuator so that they will stay in that position. That will allow you to drive the vehicle in relative comfort while you seek out a more qualified shop/mechanic to finish the repair.

What part of the country do you live in?

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