1986 k15 A/C truck under dash

[gcochran223]

86 k15 with a/c. Trying to figure out why the previous owner would attach this tie wire to the threaded piece in front of the swivel part for the vents in the dash. What does this threaded rod do and any ideas why the tie wire would have been installed. Is something missing from there and he rigged it up?the cable that moves the box below works properly but this piece of rod stuck in place has me curious. i havent ran the truck yet its still in the build stages to verify proper defrost/vent operation. i do know i need to replace the heater core which is why the dash is off, when i noticed this. im having a heck of a time finding any diagrams for under the dash for the c10 or k10s. any info is appreciated!

[gcochran223]

i was able to access the service manual and i believe i found it. i think it is 153 the part referenced "link". what does this shaft control? i was able to read up on the vacuum lines the A/C models have and i pray they are operatable. i will check to see if i have the canister in the engine bay and go from there. I'm highly doubtfull i reconnected it after the new motor. does a vacuum control this shaft? and what parts connect to this shaft and where does it connect?

[Magic1]

If I'm looking at it right that's the rod that controls the door that changes air flow between defrost/vent and such. I'm not completely sure if it's vacuum controlled because when I bought mine the po had removed all the vacuum components(why I have no idea) but I did the same thing as yours is. My door wasn't staying in place one way or another very tight so I tied it to the defrost side.

[gcochran223]

i guess worst case scenario keeping it on the defrost side forever isn't that big of a deal. its not like its a daily driver. just don't like leaving stuff rigged up when there is a chance to properly fix it.

[bd]

That adjustable link ties the mode door and blend door together, controlling the timing between the two doors for correct function of A/C & heater, so that air will blow out the dash or floor nozzles under the correct circumstances.  The mode door is vacuum actuated by a double sided vacuum motor that attaches to the front side of the heater housing, sandwiched between the housing and the firewall.

If the rod is popping loose regularly, either it is not adjusted correctly or there is something loose inside the housing that is interfering with the blend door.

[gcochran223]

bd i sent you a PM

[bd]

Item #
145 = cable operated "temp" door
166 = vacuum actuated "defrost" door
171 = vacuum actuated "mode" door
157 = (hinge) shaft for mode door
163 = link actuated "blend" door
160 = (hinge) shaft for blend door
153 = link connecting shaft 157 to shaft 160

All of the cabin air passes through the evaporator core.  The mode door (171) directs air flow out the dash vents (Vent & A/C), or onto the floor (Heater), or both (Bi-Level).  The blend door position inside the heater housing (163) determines whether air passes through or around the heater core.  The position of the blend door is timed to the position of the mode door by adjusting the link (153) that connects the two doors together.  The temp door (145) controls the volume of air passing through the heater core, hence the outlet temperature.  The defrost door (166) redirects 'floor' air onto the windshield.

[gcochran223]

Excellent bd. I should fully understand the air flow after all this. It gets awfully cold in new Ohio so I kinda wanted everything proper. I noticed the vacuum lines are missing on some so that's a whole new ballgame. Thanks for the help.