2003 Tacoma SR5

When I turned on the heat this AM, I could not get the air flow to change from the windscreen vents to any other place (dash or feet). The knob rotated freely, but the HVAC doors clearly weren't moving. The fan worked fine at all speeds and the recirculate button and the resulting intake airflow re-direction worked fine.

After about an hour, the system came back to normal by itself.

I assumed that I had lost a vacuum line (since the recirculate door appeared to work and because all electrical controls seemed to work). However, I do not see how a vacuum problem could fix itself.

I have not tried a cold re-start yet (still at work), but I would like to fix the problem even if it does not occur again right away.

 

not sure but I think the recirculation is manual either way they should be on two different vacuum lines and one could have gotten slightly clogged and the obstruction broke free.
What Temperature was it?

 

It was about 20F outside. My feet were still chilly 50 minutes into the ride, so I guess that temp under the dash could have been cold for most of my one-hour drive.

 

My 2004 does that occasionally, and I found there is a lever behind the panel just above the transmission tunnel that can be moved by hand - I guess, in my case, the actuator just sticks sometimes.