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Old 01-12-2015, 04:53 PM   #1
scottj66
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I'm stuck on vents only

Hello all, I'm new to grand am's and this site. I just bought a 2004 gagt and I have a problem with my hvac selector switch. All the air comes out of the vents, with a little coming out the floor and defrost. From what I've read, I think it's a vacuum problem. I can't find a vacuum schematic to try and find the leak. Does anyone have one, or am I wrong in my diagnosis? Any help would be greatly appreciated, and thanks in advance.
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Old 01-12-2015, 07:53 PM   #2
bricooper78
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The vacuum lines on the back of the switch are a silicon type of stuff.... I had 1 about halfway off and it did that, so just pull the center bezel (around the radio) off, and take the bolts out of the HVAC control, and SLOWLY and GINGERLY pull that sucker out, and push those things on there 100%, if that doesn't do it, post again, haven't had that car for a couple years now, my memory is foggy of where it runs to from under the dash, but I was thinking the driver's side of the intake??
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Old 01-12-2015, 08:12 PM   #3
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Vacuum source is probably the grey plastic line connected to manifold vacuum near the FPR.
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Old 01-12-2015, 09:44 PM   #4
scottj66
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I took the controller out on Saturday. There are a red and yellow set of lines that go to an actuator, blue and green go to another, brown goes to recirculate, which leaves a purple line unaccounted for. I'm guessing this is the vacuum source, but if it is, does it splice onto the gray one somewhere? On GM service and parts operations site, there is a vacuum control system diagnostic section that mentions a vacuum reservoir tank. Does anyone know where that is located? I removed the vacuum lines from the controller, and with the engine running did not hear or feel any vacuum. I just hope I don't have to pull the dash to fix this. Thanks for the help so far, I appreciate it.
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Old 01-12-2015, 09:59 PM   #5
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Oh hell yes!!! that triggered it

okay there is the little canister looking thing, like 5 bucks at o'reilly.

it sits above where your right knee will be when you're sitting and driving. take the lower panel off (the black under your dash panel) and it's right there. flat, UFO shaped thing and you'll see the couple hoses coming out of it. i forgot about that!
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Old 01-13-2015, 06:57 PM   #6
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Violet hose goes to vacuum reservoir. The reservoir will have a source hose (probably the grey line from underhood). If no vacuum is present at the violet hose nipple on the reservoir with the engine running, remove the source line to test. If vacuum is present on the reservoir's source hose with engine running, replace the broken vacuum reservoir and retest; if no vacuum is present, trace and repair the source line.

If vacuum is present at the purple hose nipple on the reservoir, resume inspecting for damaged vacuum lines/actuators at the heater case, a faulty HVAC controller and ink pens stuck in mode door.
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I'm pretty sure you don't need 600HP to merge safely onto a freeway. and if you do, you're doing it wrong.
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how do you think i ever got girls to show up? i'm only paying for so many of them
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Old 01-13-2015, 08:17 PM   #7
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I'm going to tackle this Saturday when I actually have time. I'll post up after I get it fixed. I really appreciate the quick and detailed responses. Thanks!
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Old 01-19-2015, 05:58 PM   #8
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I started disassembly fri. night after work. Bricooper78, I think you are thinking of an actuator, because the vacuum reservoir tank is way up in there. I can't even get my hand up in there, unless I would unbolt the brake pedal. I also pulled the glovebox out to see if I could get to the other end of the tank and I can't even see it. So it looks like my dashpad has to come off to get this fixed. I did a search on dash removal and didn't find anything. Did anyone ever do a how-to on that? Once again, thanks for the help.
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Old 01-19-2015, 06:55 PM   #9
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Ah you're right... It's been a while since I had a GA, my bad dude.

I'll dig around on as S10 forum, there is a guy who put a GA dash in his S10 for some crazy reason, I think he had a really detailed thread IIRC
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Old 01-19-2015, 10:01 PM   #10
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It would be wise to do as much trouble shooting as possible in situ; several of the HVAC components are easily replaced...after the dash is out.
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Quote:
Originally Posted by cardude007617 View Post
I'm pretty sure you don't need 600HP to merge safely onto a freeway. and if you do, you're doing it wrong.
Quote:
Originally Posted by bricooper78 View Post
how do you think i ever got girls to show up? i'm only paying for so many of them
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Old 01-21-2015, 04:51 PM   #11
scottj66
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I checked out gm parts direct and the vacuum tank is no longer available. Is it really necessary, or can I just hook the vacuum lines together? I'm half tempted to just get a 12 volt vacuum pump and hook directly to the purple hose on the back of the hvac controller. Then I wouldn't have to pull the dash. I guess I'm really looking for opinions or other ideas.
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Old 01-22-2015, 06:07 PM   #12
plastic_indian
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The vac res is actually faulty??

Eliminating the reservoir may cause the HVAC to change modes without driver input during low manifold vacuum conditions (i.e., heavy acceleration).

A separate vacuum pump could be functional, but will noisy to the point of annoyance; later medium duty GM trucks (C4500-C6500) used a 12v pump and it was located on the side of the core support.
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Quote:
Originally Posted by cardude007617 View Post
I'm pretty sure you don't need 600HP to merge safely onto a freeway. and if you do, you're doing it wrong.
Quote:
Originally Posted by bricooper78 View Post
how do you think i ever got girls to show up? i'm only paying for so many of them
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Old 01-24-2015, 07:49 AM   #13
scottj66
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I'm not sure if it's faulty, but just want to have everything in hand and ready to swap when I do it. This is my daily driver and has to be ready to drive to work on the Monday after whatever weekend I do this on. Today I'm going to unbolt the brake pedal to get my arm up in there and see if I have vacuum on the grey source line. If I do, then it's dash removal time.
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