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10-11-2021, 12:57 PM | #1 |
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Join Date: Feb 2009
Location: Fleming Island, Florida
Posts: 14
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A/c Flapper Issue and Power Window Issue
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. |
10-11-2021, 02:00 PM | #2 |
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Join Date: Feb 2000
Location: Maquoketa, Ia/ Orr, Mn
Posts: 3,051
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Re: A/c Flapper Issue and Power Window Issue
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.
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'51 South Bend Model "9A" '56 Chevy 3600 NAPCO '74 Chevy Cheyenne Super K20-restored on 37's '72 GMC Sierra Custom K2500- in progress '08 GMC Envoy Denali '12 GMC Sierra 2500HD Denali '17 GMC Yukon XL VCCA member #58596 http://www.nohrco.com |
10-19-2021, 09:35 PM | #3 | |
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10-19-2021, 11:20 PM | #4 |
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Join Date: Oct 2015
Location: Ottawa, Ontario, Canada
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Re: A/c Flapper Issue and Power Window Issue
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.
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1977 REG cab Long Bed with a 1984 Front Clip, 82 305 .60 over 9.0.1 flat top pistons, 4bbl, TH350, w/84 SS-intake & cam , w/ 1977 big block rad, 1975 gear box, 1984 master w/ metric fittings top & SAE fitting @ portion block, 1975 3.42 gear open diff. Duel 77-87 Factory air cleaner, duel inlet from rad support . Down sized 9' to new 8' Steel flat bed Was a 77 454 w/308 gear. Taken out 550 lbs. up front with motor clip change. |
10-20-2021, 12:36 AM | #5 |
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Join Date: Jun 2011
Location: Central OR
Posts: 728
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Re: A/c Flapper Issue and Power Window Issue
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1955 GMC 250 8 Flatbed 1971 C30 157" 350 4spd 10' Flatbed 81 GMC K30 CnC 9' Flatbed 454 T400 89 GMC Jimmy Stock https://67-72chevytrucks.com/vboard/...d.php?t=810958 71 LT1 Convertible, 72 Coupe 69 CJ5, 75 CJ6, 67 M715, 72 M35A2 Bobbed, 95 XLC2 |
10-20-2021, 07:18 AM | #6 |
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Join Date: Aug 2012
Location: Oklahoma City, OK
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Re: A/c Flapper Issue and Power Window Issue
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. |
10-20-2021, 08:39 AM | #7 |
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Join Date: Feb 2000
Location: Maquoketa, Ia/ Orr, Mn
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Re: A/c Flapper Issue and Power Window Issue
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.
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'51 South Bend Model "9A" '56 Chevy 3600 NAPCO '74 Chevy Cheyenne Super K20-restored on 37's '72 GMC Sierra Custom K2500- in progress '08 GMC Envoy Denali '12 GMC Sierra 2500HD Denali '17 GMC Yukon XL VCCA member #58596 http://www.nohrco.com |
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