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I had trouble with the C68 HVAC in my '96 coupe recently. All the air blew out the defroster and floor vents, none from the front vents regardless of the mode selection on the control panel. Yes, the check valve on the engine was bad, fell apart in my fingers, but replacing it did not fix the problem. The problem is in the connector that runs the vacuum lines from the HVAC Programmer into the flapper door dashpots on the plenum. This connector is held on by a push-nut (really nice to remove where the programmer is installed), and holds 5 vacuum lines: one source line from the engine and four lines to the dashpots. In my car, it appeared that the connector was not fully engaged, resulting in a vacuum leak. I inspected the connector, tested the Programmer (it's okay) and reinstalled the whole works, replacing the push-nut with an elastic stop-nut. And the problem remained! I then separated the vacuum connector and re-connected the two halves with 5 pieces of clear tubing. This fixed the problem, so I know that the bug is in how the two halves of this connector mate together. It could be possible that the vacuum source is getting blocked off by the connector somehow. I still have not figured it out entirely. I'll add more to this thread after I figure it out. In the meantime, if any of you C4 contributors know the quirks of this connector, let's hear!
I went through this crap when I first got my 96, I did EVERYTHING to try to make the darn thing work the way it's supposed to. After I thought I had it fixed it worked for like a month and then went to the crapper again.
I know you're right about the vacuum headers under the dash, when I mess with those it starts to work and then a few days later it fails again.
I have no fix and gave up on the dam thing, I only drive it in the summer and it's usually with the windows down so I just live with it for now.
Someday I'm gonna find a 100% absolute fix for this POS engineered vacuum header thing and give it away for free to stop the insanity.
every 96 has this problem, and I'm tired of hearing about the vacumme thing under the valve cover.
I had my seat out, my back twisted in there, removed the connector, & controller box, put it back on with a real nut, and still not fixed.
IIRC, I have vacumme at the black vacumme hose.
luckily it's a track car, so I havn't played with it too much since....
I have this same problem on my '96 CE LT4. Has anybody converted to an either a manual A/C controller or one of the Auto A/C controllers from an earlier year? This problem drives me crazy!!
I almost have the same problem in mine, the air begins out the defroster and floor vents and then moves to the front vents after a minute or longer. Does anyone know if the 95's have the same setup? I never hear of anyone having this problem with a 1995....
From what I've heard/read, the A/C programmer for '96 was a one-year deal. I'm not sure what the '95 to '96 changes were - I think if there were some way to adapt a '95 programmer to work it might solve the problems.
Yep, just bought this Grand Sport and am having exactly the same problem - AC comes through heater or defroster vents for approx 3 - 5 minutes before coming out proper vents.
I found a used controller on ebay for $40.00 but it was probably for sale for the same reason.
I'm trying to understand exactly what you did to fix yours - is this connection you repaired on the controller where the tubes plug in?
Also, is the contoller under the driver's side dash on the right side? How hard is it to get to?
Thanks,
Bob
The programmer is under the dash on the driver's side - on the firewall tucked up behind the gas pedal. Getting to it requires a few yoga classes and some acrobatic talent.
As far as the fix goes - how's your progress bvsmith?
Yep, just bought this Grand Sport and am having exactly the same problem - AC comes through heater or defroster vents for approx 3 - 5 minutes before coming out proper vents.
I found a used controller on ebay for $40.00 but it was probably for sale for the same reason.
I'm trying to understand exactly what you did to fix yours - is this connection you repaired on the controller where the tubes plug in?
Also, is the contoller under the driver's side dash on the right side? How hard is it to get to?
Thanks,
Bob
This is normal operation if you read the service manual, this makes it doubly hard to fix this dam thing because you have to wait at least five minutes before you deem your fix not worthy or a fix.
I had some success with cutting back the little **** on the programmer side of the vacuum manifold and using a slight amount of dielectric grease to seal the vacuum fittings there.
That worked for about a month and then it decided to go right back to defrost and heater vents only again.
I believe the problem is that the tips for each vacuum line is too soft and so the vacuum pinches off the flow, so the air flow never gets diverted from the defroster which is the default position.
I have tried cleaning these ends, but like others, works for a few times, then back to "normal" operation.
The fix would be to replace those soft ends with something else...or put a small tube into the soft ends to keep them open but still allow the vacuum connector to mate and seal.
Anyone have access to some very small brass tubing?
I bought a new A/C Programmer thinking that my old one was bad and this new one would do the fix. Nope. I am back to square one and the last 3 months I said blank it. I just can't figure it out. Everything is hooked up solid and it's just not blowing. I bought a new blower control module and a new blower motor. The evaporator is cleaned and not plugged up like one member's here.
To change the A/C Programmer you have to pretty much stand on top of your head to see it and to get to it. Pull the seat all the way back, tilt the wheel up, take out the floor mat for your knees, lie on your back and put your head where the pedals are and look straight up and you'll see it on the firewall. I believe there's one bolt holding it onto the firewall. Next you pull the vacuum hoses from the programmer to remove the A/C Programmer. Good luck and if your like me and don't really know what your doing, I'd get somebody that does. You'll be sore for about two days later BTW.
I fixed my '96 Grand Sport's HVAC gremlin yesterday, and the problem is the manifold connector on the '96 HVAC controller.
Photo 1 shows the manifold connections on the '96 controller. Notice how the plugs are very soft. They appear to be so soft that they are collapsing under vacuum.
Photo 2 the manifold connectors on a controller I purchased for $40.00 on ebay, unsure of what year it is. Notice that the connectors on this one are hard plastic. Not knowing the compatibility of this controller to my '96, I just removed the manifold connector and swapped it into my controller unit. I used a locknut to screw it down.
AC immediately comes from proper vents now, and all other functions work properly.
bvsmith and LannyL81 (above) correctly identified this connection as the culprit. I believe one could clip the soft tips back on the stock controller and also possibly alleviate this problem.
Old controller I bought on Fleabay
Inside controller showing tubes going to manifold
Newer controller with manifold swapped
Last edited by Digital Disaster; 08-07-2017 at 07:16 PM.
Digital Disaster got it right, the '96 uses the vacuum connector with the soft tips. These apparently close up under vacuum. What I did to fix this problem was to remove the vacuum connector entirely, both halves. I bought a 6' lenth of 7/64" ID rubber vacuum hose and cut five 6" lengths, This hose fits tight over the hard plastic vacuum lines that are used in the HVAC system. I then went inside the programmer and slipped one of the pieces of rubber vacuum hose over each of the colored vacuum lines, and then marked them with the color of the vacuum line. I re-installed the programmer, and then connected the other end of each piece of rubber vacuum hose to the vacuum line that had the same color as the label I put on the rubber hose pieces. It's just a simple splice, really.
Now the vents all work perfectly. The switch between floor outlets and front outlets happens in 3-5 seconds.
Now, given what DigDis showed, I might have tried to just cut off the soft tip of the half of the connector that's in the programmer. Then the connector would be more like the earlier models. But, there is one remaining problem. You can't tighten the nut too far, or the connector will bottom out and seal off the vacuum anyway. And if you don't tighten the nut enough, one of the nipples might not get together with it's other half, resulting in a vacuum leak. Altogether a really poor design, in my opinion. I'm happy with my fix.
In addition to the two fixes above, I can confirm another solution that worked for me. I disassembled the vacuum connector and cut the soft rubber tips off the vacuum plugs. The module was reinstalled in the car using a longer bolt, lock nut, and a standard nut to secure the vacuum connector to the module. So far everything works as it's supposed to (knock on wood).
how in the hell did you guys get to this thing? I spent all afternoon worming my way up under the dash and then dont have room to move. Is there anything I can remove to make this easier? I am about ready to pull the dash..............
Thank you everyone! I've had my '96 CE LT4 for over 7 years without a properly functioning HVAC system. It was a royal pain in the keister, but I now have a functioning system! I clipped all of the tips of the nipples down about 1/8" and put it back together using a nut and washer in place of the push on nut. (I used a small pair of snips to get the push nut off by the way.) I greased all the nipples up with dielectric grease and put it all back together. And miracle of miracles... it works! Now to go get the AC system checked and recharged!
L82Shark - I didn't remove anything other than the lower dash and I spent several hours laying on my back with both hands up in there jacking with stuff. It is a royal pain, but I got it done.
I also just fixed the HVAC controller on my '96, although I went about it a little differently. After getting the two halves apart where they join at the controller (took awhile I must say), I cut the colored tubing at the connector where it goes to all the diverter doors and removed the controller from the car.
Undid the bolt that holds the other half of the connection on the HVAC controller. Took the header assembly out of the controller and cut the tubing at the connection block. Now, this eliminates any connection on the controller itself.
Now here's where you can save yourself lots of time on your back. Cut the colored tubing close to the connector before you even get started! Then you can remove the controller with both halves of the connection attached. If I had known I was going to do the repair the way I did, I would have definitely done this. There's no need to separate the two halves while your upside down in the car!
I used 5 pieces of 3/32 ID tubing, each cut 8 inches in length. Connected each piece of tubing to the five colored tubings coming from the header. Replaced the header in the controller and fed the new tubing directly through the holes in the controller. Marked each open end of the new tubing with the corresponding color, sprayed a little CRC in each end and placed the controller back in the car. After that, it was as simple as matching the colors to the new tubing.
No worrying about collapsing tips or matching up the two halves of the connection and then trying to make sure it's tight enough. Yes, the A/C now comes through the vents and I no longer have icicles on my windshield.
Another word to the wise... Remove your driver's seat. It's easier on the back, but a little tough to get out of the car. Make sure someone's within yelling distance!
I recently bought a 1996 Polo Green / Tan convertible and post purchase discovered the dreaded HVAC problem. I came across this thread and the pictures were so helpul.
Here is what I did:
1) Unbolted the controller unit from under the dash
2) Seperated the controller and manifold by removing the one way nut
3) Cut off the soft rubber tips on the controller unit
4) Replaced the bolt in the contoller unit with a longer one to allow for a screw on nut
5) Reattached the manifold to the controller and secured with a nylon lock nut
6) Reinstalled the unit under the dash
7) Tested the unit and it worked properly!
Thank you for all who posted. I hope to be able to return the favor in the future.
10-02-2006, 01:02 PM
'96 HVAC Vent Control Problem
Now to go get the AC system checked and recharged!
