AC doesn't blow as much as it should

[Harmon]

1986 Chevrolet C10 350

AC works and blows on all 4 levels.  However it does not blow as much air as it should.

I have messed with the rod and metal "hinge" on top of the heater core box on the passenger side under dash.  I can push the rod toward the drivers side and I experience quite alot more air coming out the vents.  However when the rod is in the plastic clip connected to the "hinge" it doesn't move or allow the rod to move to the DR side allowing more air.

I do not know if I am missing a part. 

Could this be do to insufficient vacuum?  Is there only one line going through the firewall to engine hooking up to the vacuum?

[VileZambonie]

MAX AC setting is the recirculation mode and closes off the air door at the cowl.

[Harmon]

When it is on MAX AC it blows cold air, but it doesnt blow very hard.  When I push that rod under the dash on the top of the heater box, it blows harder. 

Not sure how to do all the adjustments, and how that rod moves?

[MIKE S]

Take the front distribution duct off off the front of the case. Left of center of glove box. 2 bolts on bottom. 1 to upper distribution duct. First you have to remove the lower crossover duct that goes to the far left side of dash. Slide duct down from upper retainer. Look at the mode door. It has a rod attached to it coming from inside the box. The plastic retainer may be broken and not  allowing the door to open all the way. If that is the case I have seen people get creative and attach a piece of metal to the door to make the rod work. The plastic retainer is now being reproduced and can be bought from some of the catalogs. You also may have a lot of dirt stuck to the evaporator. Pull out resistor and look. You put a garden hose nozzle in there and wash it out.

[bd]

Referring to the diagram, the threaded rod to which you refer (#153) is an adjustable link that connects and times the motion of the slave operated bi-level baffle (aka, blend door - #163) to the vacuum actuated mode door (#171).  To adjust the door-baffle timing, separate the bi-level baffle slave link (#153) from the nylon split connector (#154) that protrudes from the top of the bi-level baffle shaft (#160) by lifting upward on the link.  Physically rotate the mode door shaft (#157) all the way CCW by pushing the mode door (#171) inward against spring tension to its stop and hold it in that position.  Next, rotate the bi-level baffle shaft (#160) all the way CW to its stop and snap the threaded slave link (#153) downward into the nylon split connector (#154) locking the baffle to the door.  Reassemble the ducts and you're done.

The neutral position spring (#159) and adjustable bracket (#156) simply adjust and retain the mode door and bi-level baffle in their neutral or rest positions.

Hopefully, I'll get around to adding a detailed write-up on this topic to the Technical Forum before too long.

A notably beneficial and easy upgrade to enhance airflow once the doors/baffle are properly adjusted is to substitute a mid-90's blower motor from a subsequent body style C/K series truck.  They move a lot more air.

[Harmon]

Ok, I got it all hooked up and working properly  now.  Thank you all!