WildBill66 did pass the time by typing:
> I own a 1994 Grand Cherokee and the AC air mixture door sticks sometimes
> and will mix hot and cold air for a few moments, then I hear a
> light thump and the door closes and cold air comes out the vents.

Sometimes the sealing foam tape they use comes loose and gets in the
way of the door, or the vac motor gets obstructed either by dirt or
by a wire bundle coming loose and resting on it. But more often than
not it's a vac leak on the engine side.

> I think the linkage that controls the door is sticking and it is dirty
> with debris around the linkage. Where is the linkage control located on
> the Grand Cherokee and what does it look like ? The underside where the
> floor vents is where the door is located, but I cannot se the linage like
> I could on older autos.

Like all things ZJ, they are hard to get at.

> I see a small bell shaped cylinder with a line going into it, but I'm not
> sure what is is. The part in under the drivers side near the center where
> vents branch out from main duct.

That's the heat/defrost door actuator

Here are the rest.

Recirc door air actuator.
This pain in the butt is located above the blower motor on the
firewall side of the HVAC unit.

Panel/defrost actuator.
Drivers side of the HVAC unit about in line with the VIC. Not sure
But I think you can get to it by taking the VIC out. It's been a while.

You might have a slight vacuum leak and it's taking that long for the
vac to build up and finish moving the door.

As old as your ZJ is, I'd be checking all the vac lines under the hood.

--
-- DougW -- 93 ZJ 4.0 http://members.cox.net/wilsond
HESCO Supercharger - 300W IASCA Stereo - Edelbrock IAS Shocks
Gibson Exhaust - rear DCpower - custom gauge install - Stillen Rotors
Banks Header - and BEER, in the fridge!