Electronic Air/Heat Control Continous Cycling
#1
05-11-2008, 10:39 PM
Electronic Air/Heat Control Continous Cycling
99 Blazer/4 Door/2WD/91,000 miles
After a dead battery, my Electronic Air/Heat control will only cycle back/forth between full heat and A/C. I have read about the "reset" method of removing the B+ power, via fuse removal and re-install. I've followed the procedureseveral times, to no success. I've also connected the a Code Reader and found zero codes being induced. I can tell that the A/C and Heat are functioning. The cycling of heat and A/C occur no matter what settings that I chose (Auto or Manual). The only things that seems to work correctly is the Off position of the blower, as well as the manual on/off of the Inside/Outside air and manual A/C on/off selection.
Does anyone happen to have any suggestions for what to try next? Could the control panel be deffective?
ANY suggestions are certainly welcome!
After a dead battery, my Electronic Air/Heat control will only cycle back/forth between full heat and A/C. I have read about the "reset" method of removing the B+ power, via fuse removal and re-install. I've followed the procedureseveral times, to no success. I've also connected the a Code Reader and found zero codes being induced. I can tell that the A/C and Heat are functioning. The cycling of heat and A/C occur no matter what settings that I chose (Auto or Manual). The only things that seems to work correctly is the Off position of the blower, as well as the manual on/off of the Inside/Outside air and manual A/C on/off selection.
Does anyone happen to have any suggestions for what to try next? Could the control panel be deffective?
ANY suggestions are certainly welcome!
#2
05-12-2008, 07:47 AM
RE: Electronic Air/Heat Control Continous Cycling
A typical code reader will not access the HVAC system. To read the codes, you must have a Tech2 or equivalent (autoenginuity, snapon, etc) scan tool with bi-directional controls and the proper programming to access the various subsystems through the class 2 serial bus that are outside the generic OBD2 standard interface.
There are two possibilities for failure, the blend door motor itself or the control module. Without running functional checks via my scan tool, I would not be able to tell you which it is. The B+ reset method does take some time to calibrate the blend door in some cases... How long have you allowed it to work before changing settings on the control module?
For Automatic Climate Control models:
The RDO BATT fuse disconnect should also recalibrate the manual control version.
B+ is the battery positive.
There are two possibilities for failure, the blend door motor itself or the control module. Without running functional checks via my scan tool, I would not be able to tell you which it is. The B+ reset method does take some time to calibrate the blend door in some cases... How long have you allowed it to work before changing settings on the control module?
For Automatic Climate Control models:
Re-Calibrating Actuators After Power Loss
Calibration of the Electronic Climate Control (ECC) module occurs whenever B+ is removed and then restored to the ECC module. During this calibration process the ECC module will automatically command the temperature door to the full HEAT position and then to full COLD position. The ECC module records both the minimum and maximum door positions and uses this data, which is in counts, to determine temperature door settings based on customer selected temperature settings.
IMPORTANT: Do not select or use the scan tool HVAC menu during the ECC module calibration period or the ECC module will not calibrate properly.
If the ECC module has been interrupted by scan tool operation the temperature door will become inoperative. If this should occur then:
1. Turn the ignition switch to the OFF position.
2. Disconnect the scan tool from the Data Link Connector (DLC) .
3. Remove the RDO BATT fuse for 10 seconds and then reinstall the fuse.
4. Place the ignition switch in the RUN position and wait 40 seconds for the ECC module to initialize.
Calibration of the Electronic Climate Control (ECC) module occurs whenever B+ is removed and then restored to the ECC module. During this calibration process the ECC module will automatically command the temperature door to the full HEAT position and then to full COLD position. The ECC module records both the minimum and maximum door positions and uses this data, which is in counts, to determine temperature door settings based on customer selected temperature settings.
IMPORTANT: Do not select or use the scan tool HVAC menu during the ECC module calibration period or the ECC module will not calibrate properly.
If the ECC module has been interrupted by scan tool operation the temperature door will become inoperative. If this should occur then:
1. Turn the ignition switch to the OFF position.
2. Disconnect the scan tool from the Data Link Connector (DLC) .
3. Remove the RDO BATT fuse for 10 seconds and then reinstall the fuse.
4. Place the ignition switch in the RUN position and wait 40 seconds for the ECC module to initialize.
B+ is the battery positive.
#3
05-18-2008, 09:27 AM
RE: Electronic Air/Heat Control Continous Cycling
HOORAY - WORKING AGAIN!
I have the vehicle Service Manuals and followed the instructions several times, to no change. This morning, I decided to try something different. While the engine was running, I pulled the B+ fuse, waited approximately 30 seconds. During this time, I could hear the vacuum pulling doors open, or closed. Then, while still running, I plugged the fuse back in. Immediately, the A/C began working correctly....oh, so nice to have A/C in South Florida again!
I have the vehicle Service Manuals and followed the instructions several times, to no change. This morning, I decided to try something different. While the engine was running, I pulled the B+ fuse, waited approximately 30 seconds. During this time, I could hear the vacuum pulling doors open, or closed. Then, while still running, I plugged the fuse back in. Immediately, the A/C began working correctly....oh, so nice to have A/C in South Florida again!
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