AUIII Fairmont climate control way out

[rowan194]

I noticed last night that my vents were blowing out air that was barely perceptible as "warm," even when set to 32C and a fan speed of 10. At first I thought it was my coolant being a bit low, but a topup made no difference. Was starting to wonder if the AU also suffered issues with the blend door, maybe mine had broken (happened in my EL). Then today I tried manually resetting the CC unit, voila, now it blows out HOT air again.

How can the calibration or whatever drift so far off that a soft reset is needed? I've seen the external temp reading go out before (once it showed -7 when it was actually about 15 degrees) but nothing seemed amiss on the display this time. Something was telling it that the ~20C air coming out of the vents was 32...