cvc is making me think more about the air mix door actuator gear breaking.

I know many have experienced the air mix actuator failing and we all know it'* related to the plastic gear breaking internally.

Usually this occurs after the battery is unhooked and then reconnected. My theory at this point is that when the battery is disconnected the ECC doesn't know where the door was and tries to push the door upon restart to full hot or full cold.

Has anyone ever found anything in the manuals that tell us we should unhook the actuator rod in cases like this, or set the air to full cold before unhooking the battery.

I'm thinking there'* at least one way we can keep from possibly breaking actuator gears for the restart.

Thoughts.

Interesting theory. I have never found anything in the FSM that indicates doing anything with the ECC before battery disconnect, but it certainly would seem like a very good explaination. I mean, we have had a couple of instances where this has happened after battery disconnect. How else would a battery disconnect lead to the breakage of the gear in the actuator?

I think the plastic in the drive gear may get brittle after time, adding to the problem. The programmer has the ability to run a self calibration, I’ve watched it. If the ECC is flashing calibration code, the controller will run the door all the way to the left (cold), then all the way to the right (hot), then try to adjust the temperature to the ECC setting. When the battery is disconnected, I’m sure the controller dumps its memory just like you speculate then enters the cal routine to get back to a known location. There are no limit switches, sensors, or other gizmos that tell the controller that the door is fully open or fully closed (full hot or full cold). How does the programmer know when the door should be at it’* travel limit? I don’t think it does. I think it’* told, based on gearing and other parameters, how long it should run in order to drive the door from one stop to the other. Or maybe it senses a load on the motor, indicating the door won’t move any farther. (Problem with this is that you’d think if it never met with resistance (i.e. the gear is split), the motor wouldn’t stop. But it does.) Either way it has to drive the door to its limit so there will be a period of time when the motor is torquing the gear.

I wonder why the gear splits, but doesn’t strip any teeth?

I'm betting on load of motor.

Yeah, but I bet there’* a timer in there too ‘cause my gear was so bad it couldn’t create any load on the motor – you’d think if load were the only parameter my motor would continue to run.

I looked for my defunct actuator last night. I was going to play with it but I must have tossed it. Odd, I usually keep broken parts laying around for 1-2 years! I had to resort to my pictures – my drive gear was almost split in half.

The actuator also has a PC board inside it, I never did take a look at that. Dang. There’* no less than 5 wires coming out of that thing, there’* more going on in that assembly than meets the eye. Wish I had a schematic of it.

This is some info that I've come across.

Actuator Description

The automatic climate control system (C6 uses the following five actuators in order to adjust the temperature and the air distribution:

* The electric actuator or the temperature actuator controls the temperature valve.
* The air inlet actuator controls the air inlet valve.
* The slave actuator controls the heater slave valve.
* The mode actuator controls the mode valve.
* The defroster actuator controls the defroster valve.

When servicing an actuator, replace parts with the 4 correct service parts for the actuator being serviced. The electric actuator for the automatic climate control system (C6 has a green R on the top in order to differentiate the electric actuator from the electric actuator used on the manual climate control systems (C42, C60).

The electric actuator contains a feedback potentiometer. The feedback potentiometer reports the position of the electric actuator to the Electronic Climate Control (ECC) module (Control Assembly). Do not test the electric actuator for movement while disconnected from the heater/vent module with the temperature **** on the control assembly. If the electric actuator is removed or replaced for service the actuator must be initialized. Refer to Temperature Actuator Replacement in Heating, Ventilation and Air Conditioning for the initialization procedure.

The air inlet actuator and the slave actuator are vacuum motors with one vacuum port in order to move the attached valves in one direction.

The mode actuator and the defroster actuator are vacuum motors with two vacuum ports in order to move the attached valves in two directions.


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.

This is at least the connector view of it. Haven't found a schematic. This information is not from the 90'* Bonneville, but I believe it to be at least similar.

...When servicing an actuator, replace parts with the 4 correct service parts for the actuator being serviced. The electric actuator for the automatic climate control system (C6 has a green R on the top in order to differentiate the electric actuator from the electric actuator used on the manual climate control systems (C42, C60)...

Well, crap. I don't remember if that one I used had a green R on it or not! Boosty? Might be another opportunity to get up in there and try some other techniques for getting that dude outta there.

Interesting information! This thing calibrates itself like a MM gyrocompass, only the gyrocompass uses an opto-electrical resolver to add the counts as it slews from east to west.

I have yet to see a green R on any of them.

Archon..what year are you getting that info from?

is the GM AC Delco number for the correct one 15-71923 ?

I uh..dunno?