I did a bit of research and this seems to be a re-occurring issue: unhooked the batteries (to do annual terminal cleaning) and now the air selector knob isn't working. It stays stuck on defrost all the time. I'm going to climb under the dash tomorrow and check the actuators, but it's very ironic how many guys have this go wrong after disconnecting the batteries!!!!!!

you have a VAC leak sir well at least that would be the case with a 6.5 equipped van .. not sure if the Dmax has the same

These units are electric servo controlled. It appears that if the battery is disconnected, occasionally the computer will 'forget' how to operate the climate control motors. Usually requires a visit to the stealer and a reprogram charge.

Usually requires a visit to the stealer and a reprogram charge.
Yup

unfortunate about having to visit the stealer's for the fix but its easier then tracing through a spaghetti pile of vac lines under the dash

Your passenger may have knocked off a vacuum line . Listen for a constant running of a little compressor , thats how we found out ours was leaking.

i second that, there's a bunch of vacuum lines just above the passenger's left foot that like to get caught