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#555261 - 04/09/08 10:42 PM A/C Blowing Out of the Defrost?  
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rmodys Offline
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rmodys  Offline
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Ft. Myers, Florida
I recently charged my A/C (R134 retrofitted, all new parts) and noticed that sometimes my A/C either only blows from the defrost and floor vents (on both A/C settings) or it blows through the defrost, floor, and dash vents. I checked all of the vacuum lines and verified their correctness using a 1986 Service Manual so I know that's not the problem.

Does anyone have any idea what could be wrong?

Thanks


1986 Monte Carlo SS. Family owned 1987-1999; 2004-present, rust-free Florida car, L69 with TPI, B&M shift kit, 3.73 posi, new PUI interior, t-tops, lowered 2", refinished stock rims, Goodmark cowl hood, and amber DRL's.
#555268 - 04/09/08 10:58 PM Re: A/C Blowing Out of the Defrost? [Re: rmodys]  
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baaboo Offline
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Racine, WI
Do you have good vacuum at the diverter valve behind the dash?


1987 Aerocoupe, 383 Super Ram and 20-gallon custom aluminum tank. Car retired (for now) from open road racing, but I'm not.
#555285 - 04/09/08 11:19 PM Re: A/C Blowing Out of the Defrost? [Re: ]  
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redlineSS Offline
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South Jersey
Diverter DOOR is probably stuck, check that out!

Dave


~Dave~
Monte Carlo...."Born on the Track, Driven on the Street"
#555306 - 04/10/08 12:01 AM Re: A/C Blowing Out of the Defrost? [Re: redlineSS]  
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rmodys Offline
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Ft. Myers, Florida
Okay so I jiggled the arm on the HVAC control panel and it started blowing out of the vents instead of the defrost.

Is it supposed to also blow out of the bottom? Or is that a fluke?


1986 Monte Carlo SS. Family owned 1987-1999; 2004-present, rust-free Florida car, L69 with TPI, B&M shift kit, 3.73 posi, new PUI interior, t-tops, lowered 2", refinished stock rims, Goodmark cowl hood, and amber DRL's.
#555435 - 04/10/08 09:53 AM Re: A/C Blowing Out of the Defrost? [Re: redlineSS]  
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84LS1T56SS Offline
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Central, Arkansas
 Originally Posted By: redlineSS
Diverter DOOR is probably stuck, check that out!

Dave


This is probably the place to start. You can see the vacuum can that operates the door in the pic. It's ALMOST impossible to change without removing the dash.




85 MCSS, 02 5.3/4L60E stock daily driver,84 MCSS, Another stock 5.3/60E.
#555449 - 04/10/08 11:38 AM Re: A/C Blowing Out of the Defrost? [Re: 84LS1T56SS]  
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redlineSS Offline
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South Jersey
There is also a vacuum manifold behind the heater control panel that may need some attention. Sometimes the head works loose from the nozzles, push it back on, and look for broken hoses.

Dave


~Dave~
Monte Carlo...."Born on the Track, Driven on the Street"
#555456 - 04/10/08 11:54 AM Re: A/C Blowing Out of the Defrost? [Re: redlineSS]  
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bug Offline
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winchester, TN
don't mean to thread jack, but I also have a simuler problem. Mine is not with the A/C but with the heater. It blows hot air out the floor vents all the time, even when the blower is not on. My father said there is a plastic arm on the blower door that might have broke. Could mine be the same problem as the one above?

#555473 - 04/10/08 01:04 PM Re: A/C Blowing Out of the Defrost? [Re: bug]  
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redlineSS Offline
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South Jersey
Clint (bug), your heater hose control valve may be shot. It is the vacuum operated valve under the hood on the heater hose line. alot of the thin plastic lines get broken from age and may not be shutting off the water flow to the heater core??

Dave


~Dave~
Monte Carlo...."Born on the Track, Driven on the Street"
#555504 - 04/10/08 02:56 PM Re: A/C Blowing Out of the Defrost? [Re: rmodys]  
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jaywos Offline
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New Jersey
 Originally Posted By: rmodys
Okay so I jiggled the arm on the HVAC control panel and it started blowing out of the vents instead of the defrost.

Is it supposed to also blow out of the bottom? Or is that a fluke?


This might be silly, there is the little vent below the steering column. I believe a hose connects to this vent. Mine was not connected and would always get cold air to my feet. re attached and now it blows out of the vent. The hose is in the nest of wiring i think.




1987 SS
#555518 - 04/10/08 04:12 PM Re: A/C Blowing Out of the Defrost? [Re: jaywos]  
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The Cadillackid Offline
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The Cadillackid  Offline
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columbus, ohio
the HVAC control panel itself might be bad... the biggest thing that selector arm does is open and close vacuum ports as you slide it.. if the "vacuum valve" is loose it will allow vacuum to go places it shouldnt resulting in erratic operation...

also there is a round "connector" omn the back of the HVAC control that often pops loose creating vacuum leaks.. esp if you have worked beind it - ie putting in a radio etc..
-Christopher


1988 LS, 385,edelbrock performer RPM and holley SA 770 carb, Headers,Duals,flow 40's, Gforce X-member, 2004R, Kevlar clutches ,Sonnax Servo,3000 Stall,3.73 Posi,Vette Rallies, Eagle GT II's, Nordskog Digital Dash, Mark VIII Fan, Ice Cold A/C,!Rebuild in progress!
** New 475HP Stroker SBC up and running!! and fryin Tires! **
#555649 - 04/10/08 10:06 PM Re: A/C Blowing Out of the Defrost? [Re: jaywos]  
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rmodys Offline
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rmodys  Offline
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Ft. Myers, Florida
 Originally Posted By: jaywos
 Originally Posted By: rmodys
Okay so I jiggled the arm on the HVAC control panel and it started blowing out of the vents instead of the defrost.

Is it supposed to also blow out of the bottom? Or is that a fluke?


This might be silly, there is the little vent below the steering column. I believe a hose connects to this vent. Mine was not connected and would always get cold air to my feet. re attached and now it blows out of the vent. The hose is in the nest of wiring i think.
Nahh, it's coming out through the center and on both sides. I might have to check out the connections on the HVAC control panel. Thanks guys


1986 Monte Carlo SS. Family owned 1987-1999; 2004-present, rust-free Florida car, L69 with TPI, B&M shift kit, 3.73 posi, new PUI interior, t-tops, lowered 2", refinished stock rims, Goodmark cowl hood, and amber DRL's.
#555773 - 04/11/08 01:24 AM Re: A/C Blowing Out of the Defrost? [Re: redlineSS]  
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86ttop Offline
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86ttop  Offline
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Brooksville, Fl
 Originally Posted By: redlineSS
Clint (bug), your heater hose control valve may be shot. It is the vacuum operated valve under the hood on the heater hose line. alot of the thin plastic lines get broken from age and may not be shutting off the water flow to the heater core??

Dave


Just an FYI, the heater valve only shuts off flow in the MAX A/C position.

You have a broken/misadjusted arm like your Dad said. Take everything out of the glove compartment and take the screw out of the retainer cable and let if fall all the way down. Look in the opening and operate your temp cable and watch to see if it operates the arm and the rod for the blend door. Good luck with your repair.



Leo Paugh
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POW*MIA
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If things improve with age, I must be approaching magnificent. thumbs
#555945 - 04/11/08 04:41 PM Re: A/C Blowing Out of the Defrost? [Re: 86ttop]  
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DLV555 Offline
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DLV555  Offline
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Findlay, OH USA
I've had this problem with my A/C since I bought the car in Jan. '07. All of my vac line are good and I have manually supplied vacuum to the individual motors and they work, so in my case it looks like my A/C control head has taken a dump. Hopefully I'll get that fixed this year before it get too hot...and then maybe also tackle the A/C leaks that I have too! If all of your vac motors work when you supply vacuum, and all of your vacuum lines hold a vacuum then I would suspect the control head.


1987 Monte Carlo SS, 400 SBC, 800 cfm Q-Jet, Edelbrock RPM Q-Jet intake, Howards Rattler cam, Flowtech headers, 2.5" dual exhaust, Delta-Flow 40s
1998 Cadillac Eldorado
1991 GMC Sierra 1500, 355 w/ Edelbrock cam, headers
1973 Mercury Montego MX, BBF 460, AirGap Intake, 800 double pumper, low ratio C6, 9" posi, 3" exhaust, Flowmaster 40s(the wife's)
#558432 - 04/18/08 01:00 AM Re: A/C Blowing Out of the Defrost? [Re: DLV555]  
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Don85SS Offline
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chicago, il
Does anyone know what color cables control what?

I have had this problem in the past and it usually works after switching between vent/heater/defrost. But recently my car was broken into and the stereo stolen now this "little trick " is not working so maybe one of the hoses is damaged.

Any tips on troubleshooting is appreciated.


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