A/c Flapper Issue and Power Window Issue

[Matt87chevy]

Hey all,

I'm having a weird issue with my A/C. I move it to any of the a/c settings and it comes out the defrost vents, but if i move it to defrost it comes out the a/c vents. Has anyone had a similar issue? Or know if it sounds like I have some lines backwards?

Also I was trying to remove one of my power window motors. The driverside is stuck in the regulator and i cannot remove it. While the passenger side clicks when going up. I've cut holes in the door to reach the motors cause they seem to go back quite frequently with the relay mod. Any advice?

Thanks.

[MJN]

In the GM service manual for your truck there is a schematic showing what color vacuum lines go to which port- easy to trace the lines and see if one is crossed or leaking. It may also be an issue with the control but I would start with tracing the vacuum lines.

[Matt87chevy]

Originally Posted by MJN

In the GM service manual for your truck there is a schematic showing what color vacuum lines go to which port- easy to trace the lines and see if one is crossed or leaking. It may also be an issue with the control but I would start with tracing the vacuum lines.

So I’ve torn this apart and looked at a few schematics. I cannot seem to interpret which lines go where, but I’ve narrowed it down to the flapper door with the plastic clip. The clip is broken, which I’ll have to fix, but I think the flap is working in reverse. Can anyone confirm that for A/C the flapper should open, but when it is in defrost mode it should close. Mine seems to be working in reverse. Any help would be appreciated.
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[Pontiac1976]

I think there is spring on the clip or cable of Vac line. If the clip is broken the vacuum may not move to a stop & let the opt sit Vac pull the open in the desired direction.
Other thing I think there's two or three vacuum balls help store Vac if they leaking or the mounting part of the line is old and cracked popped off. One in the Pass cowl vent one in the & one in the engine bay.

[farmall]

https://www.67-72chevytrucks.com/vbo...d.php?t=825569

[Dead Parrot]

Here is another thread on the subject: http://67-72chevytrucks.com/vboard/s...d.php?t=460942

Post 8 answers your heat/cold question.

No clue on the power windows, mine are all hand crank.

[MJN]

Not sure what year your truck is but on my '74 the vacuum lines are color coded and the part that connects to the dash control is numbered. The service manual will then show what color line goes to what port and also which get vacuum depending on what vent selection the control is on. I found it easier to use a mighty vac to test each line and then watch the doors open and close, then you can run the fan while you test the doors to make sure the air is directed to the correct outlets. If I remember correctly the mode door should be open when A/C is selected to route air only through the dash vents. When heat or vent is selected it will be open (or pulled toward the firewall) to allow air out the floor vent and dash vents.
This is a screenshot from the 1987 GM manual- it shows which port on the control goes to which actuator and which color the vacuum lines are. In the table the 'vent' just means its open to atmosphere and not under vacuum.