Home page
  Home Page   Contact Us   Our History   Advertise with Us   Sponsor List   Link to Us   Compare Levels   Member Agreement   Privacy Policy   About C4VR
  Community Forums   Active Threads   Forum Search   Top Posters List   Private Messenger   C4VR Email System   C4 Corvette Quiz
  Members Vettes & Pictures   Member Stories   Member Stats   Real Time Member Map   Member Search   Member Calendar Entry Form   Who's Online
  C4 Registry Data   C4 Corvette Statistics   C4 Corvette Tips & Tricks   C4 Corvette How-Tos   Corvette Club Listing   Corvette Event Listing   Mechanic Directory   Corvette VIN Decoder   Save the Wave   Corvette Emblem History
  C4 Corvette Parts Auctions on eBay   Corvette Books   C4VR In-Stock Apparel & Accessories   C4VR Member Name Badges   C4VR Custom Apparel & Accessories @ Zazzle   C4VR Window Stickers   C4VR Member Calendars   Shop Amazon.com
☰
SPONSOR AD SPONSOR AD

Topic: Air only comming out of the windshild defrostor

in Forum: C4 Cooling and Heating Systems


Already a Member? Click Here to Login

Air only comming out of the windshild defrostor

Posted: 7/30/12 10:08am Message 1 of 7
rugdoz
Standard Member
Send PM
Merritt Island, FL - USA
Joined: 8/21/2010
Posts: 24
Vette(s): 96 coupe 04 coupe
On my 96, air only want to come out of the front defrostor.  Push all the buttons and it changes nothing.  Then while driving and hitting a bump, air will come out of the selected setting point for a while then revert back to the defrostor is there a sensor or a control to check or change out?  Thanks!


SPONSOR AD:: (Our Sponsors help support C4VR)

Re: Air only comming out of the windshild defrostor

Posted: 7/30/12 11:34am Message 2 of 7
SAYWHEN
Standard Member
Send PM
Joined: 2/26/2011
Posts: 82
Sounds like you have a vacuum problem....the vacuum nipple which feeds the climate control system is on the right side of the intake under the cover which has corvette on it...there is a check valve ( has 1 line in and 2 coming out).
Check carefully all the rubber elbows,tees and plastic lines for cracks/splits any sort of a vacuum leak in this area COULD cause your issue. Does your cruise work? i ask because if memory serves one of the two lines at the check valve go to the cruise and the other to the climate control. Check all lines closely under the hood.
 
I f you find nothing under the hood.....then I'm guessing you have a problem with the programmer or the vacuum harness to the programmer. The programmer is located sorta behind the radio head unit. The programmers in these cars are known to have issues as they age. the vacuum lines in the harness itself also get soft with age also and will collapse and close up stopping vacuum flow. I f you or any one has recently done any work around the dash......ie radio replacement/ heater core etc.----it's possible one of the vacuum lines may be partially pinched and moving around when you hit a bump. I'm basing my "guess" here on the assumption that you have electronic climate control. There should be a fault tracing "tree" in your FSM for the climate control which will help with running the problem down. Hopefully I haven't confused you.Smile



Re: Air only comming out of the windshild defrostor

Posted: 8/25/13 7:17pm Message 3 of 7
jlagaipa
Standard Member
Send PM
Neptune, NJ - USA
Joined: 8/25/2013
Posts: 3
Vette(s): 1996 Coupe

I have the same problem.  Dash vents don't blow air but defroster and foot vents do work.  My cruise control also works.  I have replaced the check valve under the passenger side fuel rail.  I have read it is the AC Programmer vacuum leak due to the soft nipples and tried to fix it.

Ok this morning I attempted a repair for my dash vents that are not working.  I studied previous posts everywhere and went in somewhat prepared but apparently not prepared enough.  Please help.  First of all I didn't find exactly what I expected.  Previous post talked about pulling a push nut to get it released from the firewall.  Well upon removing the lowest sheet metal lag bolt it was free?  Upon examination I clearly see the 5 vacuum lines connected to the distributor type connector but I didn't see the soft nipples probably because I didn't pull them off nor did I remove a push nut from the center (if it is there).  On the other side I saw a cardboard type back and was able to photograph the other side with my Galaxy S3.  The whole thing looked like it had enough slack to be pulled down some (from both the electrical cable on the top and the vacuum lines) but I didn't have enough space to clear the hard vent and the steering column.  Couldn't see how to remove the vent so I thought I'd stop and ask for advice.  Looks to me that I not the first one in to this thing.  What do you think, please examine the photos below and advise in some detail.  If the links don't work then copy them into your browser.

Thanks.

 

http://collectiblesandhobbies.com/AC%20Programmer%201024%20by%20768%20110539.jpg

 

http://collectiblesandhobbies.com/AC%20Programmer%20Inside%201024%20x%20768_112614.jpg

 

http://collectiblesandhobbies.com/AC%20Programmer%201024%20by%20768%20110539.jpg




Re: Air only comming out of the windshild defrostor

Posted: 8/25/13 9:47pm Message 4 of 7
davep85c4
Former Member
Send PM
Joined: 4/4/2009
Posts: 254
You are on the right track. This is a 96-only problem.

I fixed my first one a few months ago. There are several ways to do it. Corvette Forum has a gillion threads on this 96-only issue.  I ended up cutting the lines off the connector inside the controller. I drilled out the block so 5/32 vacuum hose would go through the block. I put (5) 6" pieces of hose directly onto the colored hard lines within the controller, and passed them through the correct holes in the block. (so I'd know which one was which).  I cut off the connector in the car, and put each hard line into the respective vacuum hose extension.

It took an afternoon to accomplish, and the mode doors work properly in this car for the first time in at least 8 years.

I don't recall if I removed that hard duct in your pics. If I did, it was easy, because I don't recall any fussiness.
I did remove the electrical connector to be able to get it low enough to access the nut in the center of the vacuum connector. The threads on CF make this out to be bitchey, but I didn't have trouble with it.

What makes this a 96-only problem is that the material for the vacuum fitting nipples on the 96 controller is very soft. Over time, they suck shut, and no vacuum flows. The 90-95 controller has hard nipples that don't collapse under vacuum.
One of the other fixes is to trim just the tip of the nipple off, and remove the portion that blocks the flow.
Another fix is to insert very fine tubing (I was thinking of 18ga wire insulation) into the nipples to keep them open.


|UPDATED|8/25/2013 9:47:19 PM (AZT)|/UPDATED|



Re: Air only comming out of the windshild defrostor

Posted: 8/26/13 4:26am Message 5 of 7
jlagaipa
Standard Member
Send PM
Neptune, NJ - USA
Joined: 8/25/2013
Posts: 3
Vette(s): 1996 Coupe
Thank you Dave for your response.  I'm going to try again to get the AC Programmer down.  Aside from how did you get the AC Programmer down, where exactly did you make your cuts?  Am I understanding correctly that the 5/32 vacuum line fit over the colored vacuum lines inside and outside the AC Programmer?  Am I correct that you made your connections inside the box while you had it down in front of you, leaving six inch tails that will hang down from the box.  Then and the other set of connections had to be done under the dash with the vacuum connector pulled down as far as you can with whatever slack is available where you connected your six inch tails also hanging down? 

Please email or call me so that we may discuss this further. "jlagaipa@yahoo.com" 732 413 0337
joe



Re: Air only comming out of the windshild defrostor

Posted: 8/26/13 12:22pm Message 6 of 7
jlagaipa
Standard Member
Send PM
Neptune, NJ - USA
Joined: 8/25/2013
Posts: 3
Vette(s): 1996 Coupe
Fixed! -  All vents work as they should now!  Thank you Dave for the lead.  I fixed it the same way you have recommended except I didn't need to drill anything.  I have take photographs to help out others on this problem as follows.  You will see the programmer removed, then the quick connector cut out and replaced with 12 inches of 5/32 vacuum hoses and they connect to the existing vacuum lines that I feed out through the existing holes and then pushed onto the vacuum lines that come from the vents.  The hardest part was removing the tiny slip nut holding the connector halves together.  I used a tiny flat head to pry and then a tiny nose pliers to pull it off.  Working under the dash was a pain (literally).  I did remove the drivers seat and the lower dash cover but not the metal one.  You have to disconnect the under dash lamp and the odbii connector to fully remove the panel.   After you cut off the vacuum lines at the connector that go to the vents they don't have very much slack so it was a little difficult to push them into the 5/32 vacuum hoses that I added.  On one of them I held it with a nose pliers and push the hose in tight space.  Note the colored lines didn't go into the 5/32 vacuum lines very much, maybe 1/4 inch but it seems to be tight enough.  I did dip my vacuum hose in wd40 to help them slide.  Hope this helps folks out.....

http://collectiblesandhobbies.com/ACProg1.jpg

http://collectiblesandhobbies.com/ACProg2.jpg

http://collectiblesandhobbies.com/ACProg3.jpg

http://collectiblesandhobbies.com/ACProg4.jpg

http://collectiblesandhobbies.com/ACProg5.jpg

http://collectiblesandhobbies.com/ACProg6.jpg




Re: Air only comming out of the windshild defrostor

Posted: 5/4/25 6:51pm Message 7 of 7
Profile Pic
KA5CDJ
Standard Member
Send PM
El Paso, TX - USA
Joined: 1/17/2025
Posts: 2
Vette(s): 1992 Bright Red C4 Convertible, 1996 Torch Red C4 Convertible, 2023 Black C8 Stingray

I love the text explanation on how to repair the programmer. Pictures certainly would be helpful, but it appears that http://collectiblesandhobbies.com no longer exists.  Thanks for the effort.  1996 Torch Red LT4 Convertible.




in Forum: C4 Cooling and Heating Systems


SPONSOR AD: (Our Sponsors help support C4VR)