...and my problem, now resolved, was related to that. I wasn't aware of the calibration procedure, and because of that I likely did not follow it correctly on the first start after the battery was reconnected.
For reference, and apologies to the person who posted this on a different site which I can't find now so I can't give proper credit, the procedure to calibrate the blend doors after the power has been disconnected and later reconnected is:
- Turn the car on.
- Do not touch ANYTHING for at least 30 seconds (do not turn on the HVAC, don't touch anything).
- Done. You may now turn the car off, or turn on the heat and drive, or whatever.
This is necessary after any time the battery has been disconnected, at least if you have the system I do with the dual-zones and electronic temperature control.
To re-calibrate, if you wind up in a situation like mine, disconnect the power for at least one minute (either remove fuse 15, or since they're a pain to get to, just unhook the negative terminal of the battery for at least one minute). Then, reconnect the power, and start the car as described above.