HVAC Door Control

[Streetrod00]

Hi folks, newbie to this site but not oldies; trying to get a handle on '74 Cheyenne Super vac HVAC operation in advance of charging the A/C.  When I cycle through the various settings, all seem fine but A/C and vent.  When A/C is selected, vent door on passenger side opens and air blows through front dash openings.  When vent is selected, door on passenger side does not open.  Is this correct (perhaps a re-circ) or is one of the vac lines mis-routed on control?  New to these any any suggestions helpful.  Truck is a factory 454 w TH 400 if helps.  Thx - PM

[chengny]

[blazer74]

When A/C is selected and temp lever is full cold this is max recirc A/C and that door should be open. It's not labeled max like the later years I think starting in 76 or so.
Any other selection and that door will close.

Also when in max cold A/C  recirc the blower should be on high if it is in its original configuration with the proper blower switch and vac controls via a single orange wire to to the blower switch.
Again that if all the correct parts are there and function correctly.
If you want control of the blower speeds in max A/C recirc disconnect the Orange wire from the switch.
That's how I have mine and have control of blower speeds at all times.


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[Streetrod00]

Thanks for the help!