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| bigmoe | blowing out defrost only. | ||
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Senior Guru
 
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The air in my 94 is only coming out the defrost vents. Any ideas?
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Posted on: 2010/8/15 21:48
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| Matatk | Re: blowing out defrost only. | ||
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Webmaster
 
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Check valve. It's in the engine bay by the intake manifold attached to the vacuum lines.
Matthew |
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Posted on: 2010/8/15 22:12
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| Tre57 | Re: blowing out defrost only. | ||
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Senior Guru
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My 93 had the same issue and the check valve basically disintegrated when I attempted to pull the vacuum lines off of it. Found a replacement really cheap at NAPA.
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Posted on: 2010/8/15 22:44
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| bogus | Re: blowing out defrost only. | ||
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Grand Imperial Pooh-Bah
 
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It's on the right side of the intake manifold, between #6 and #8 injectors. It's a black thingy with 1 line in and 2 out.
Well under $5.00 at NAPA or anywhere... |
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Posted on: 2010/8/15 22:54
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| bigmoe | Re: blowing out defrost only. | ||
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Senior Guru
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Okay I'll give it a try.
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Posted on: 2010/8/16 0:26
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| pianoguy | Re: blowing out defrost only. | ||
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Guru Emeritus
 
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http://www.napaonline.com/Search/Deta ... x?R=BK_7301348_0282445003
Mine cost $200, but they threw in a nice low-profile floor jack. |
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Posted on: 2010/8/16 0:40
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1996 LT4 �Before you criticize someone, you should walk a mile in their shoes. That way when you criticize them, you are a mile away from them and you have their shoes.�- Jack Handey |
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| bigmoe | Re: blowing out defrost only. | ||
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Senior Guru
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Okay I pulled that check valve off and it seems to be okay. It's in good shape. I can blow in all the ports and it comes out the others. Or is it not supposed to do that? I put it back on. Still coming out the defrost but I noticed it also comes out the floor at the same time no matter where I set the buttons. Could the problem be something else?
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Posted on: 2010/8/16 0:55
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| pianoguy | Re: blowing out defrost only. | ||
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Guru Emeritus
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I just experimented with a spare that I had laying around. Suck on the vacuum end while blocking the other 2 inputs (this seemed to seat the check valve internals), then unblock the inputs and blow through the vacuum end - nothing should come out. It's probably worth replacing if it's suspect. Does your cruise control work OK?
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Posted on: 2010/8/16 1:39
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1996 LT4 �Before you criticize someone, you should walk a mile in their shoes. That way when you criticize them, you are a mile away from them and you have their shoes.�- Jack Handey |
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| bigmoe | Re: blowing out defrost only. | ||
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Senior Guru
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Quote:
I tried with the valve off again, attempting to seat the check valve internals. No matter waht I do I can blow through the valve. The local parts store didn't have one in stock but the guy knew just what I was talking about and showed me one on the computer. They'll get it overnight. ($11.00cdn). My cruise works. I'll post when I try the new one. |
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Posted on: 2010/8/16 23:34
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| bigmoe | Re: blowing out defrost only. | ||
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Senior Guru
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Picked up the new valve. Doing the sucking/blowing thing it functions properly compared to the old one but when I installed it I still only get air blowing out defrost and floor together no matter where I set it. Darn.
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Posted on: 2010/8/17 23:39
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| pianoguy | Re: blowing out defrost only. | ||
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Guru Emeritus
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Nuts! Well, it must be something with either the control unit in the dash, or the programmer box (under the dash, above the accelerator pedal). There is a common problem with '96 models with the vacuum manifold in the programmer box, but that shouldn't be an issue for your car. Maybe it's just contacts in the control unit that need cleaning.
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Posted on: 2010/8/18 1:51
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1996 LT4 �Before you criticize someone, you should walk a mile in their shoes. That way when you criticize them, you are a mile away from them and you have their shoes.�- Jack Handey |
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| bigmoe | Re: blowing out defrost only. | ||
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Senior Guru
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I did the fix for the control unit a while ago and all the buttons work perfect now. I'm not overly concerned about fixing the problem at this point. The a/c and heat work fine. It just bugs me when something doesn't work right and I've got everything else working perfect on the car.
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Posted on: 2010/8/18 2:52
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| 1Fast04Vert | Re: blowing out defrost only. | ||
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Elite Guru
 
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Quote:
Do you have a link for the control unit fix? Looks like I might have to do mine soon. Your present issue still sounds like a vacuum leak. Without proper vacuum the controls default to the defrost and floor vents only as a safety function. |
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Posted on: 2010/8/18 3:13
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2004 Vert. 475hp. Built by Vengeance Racing |
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| bigmoe | Re: blowing out defrost only. | ||
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Senior Guru
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Right here. I was very impressed how well it worked. When I got into mine it looked perfectly clean but I went through the process below anyway and it worked.
http://forums.corvetteforum.com/c4-ge ... ontrol-button-repair.html |
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Posted on: 2010/8/18 11:23
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| 1Fast04Vert | Re: blowing out defrost only. | ||
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Elite Guru
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Quote:
Thanks Moe, that is the link I was looking for. |
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Posted on: 2010/8/18 15:35
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2004 Vert. 475hp. Built by Vengeance Racing |
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| TommyT-Bone | Re: blowing out defrost only. | ||
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Chair-man of the bored
 
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bigmoe. Question. Are the controls for the radio working and do you have dashes in the outside temp display? I have an intermittent problem that is similar in nature. Mine just worked fine for months and just started acting up again. Last time I believe Andy pointed to my programmer. Anybody else ever have this issue?
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Posted on: 2010/8/18 19:51
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| bigmoe | Re: blowing out defrost only. | ||
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Senior Guru
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Quote:
Nope. Radio controls and display are working. No dashes on the outside temp display. |
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Posted on: 2010/8/18 20:56
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| pianoguy | Re: blowing out defrost only. | ||
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Guru Emeritus
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Here's the thread I used when I fixed my '96, but I don't think the '94 has the nipples that collapse. But there may be some worthwhile info, anyway:
http://forums.corvetteforum.com/c4-te ... vent-control-problem.html |
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Posted on: 2010/8/18 22:21
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_________________
1996 LT4 �Before you criticize someone, you should walk a mile in their shoes. That way when you criticize them, you are a mile away from them and you have their shoes.�- Jack Handey |
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| bgrant_12002 | Re: blowing out defrost only. | ||
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Guru Newb
 
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My C4 LT4 did that back in '01......fix was to replace AC programmer.....PN 16227376. Hope this helps.
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Posted on: 2010/8/23 15:34
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Transfer
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