Hello all,

My vent selections are not working properly and i am not sure where to start looking for the problem. The fan speed and Auto function seem to be working properly but it only pushes air from the defrost vent and floor vent at the same time regardless of the button pushed on the dash.........

 

hi !
just fix my i have a 96ce air would only come out the top and bottom vents for ac/and heat ,the problem is the ac/heater programer.
my freind works for chevy he did the work we order it back in oct 08
it took almost 6 months to get a brand new one from gm,finally it came in(we gave up on it)did the job couple weeks ago and everything is working like it should,this is very common in the 96 vette model.what a job to get the old one out!!!!!!!!!!good luck

 

I have a 95 and I am having the same problem. How much is the part? Where exactly is it located? Will I need to pull the whole dash apart?

 

Sounds like yours is in the default position. Remove the pass/side fuel rail cover. You'll find a vacumn valve (black) that may be the problem.

I would eliminate that possibility before buying any parts.

I think I have a photo of that valve somewhere. If interested in the photo PM with your e-mail.

 

I would definitely appreciate it, thanks. PM coming your way.

 

forgot to mention mine is a 90 vert

 

I had a '95 with the exact same problem - vacuum valve ($6 or so to replace at the time) was the problem. Fixed it with electrical tape for a few weeks until I could make it to the store.

Lift up rail cover and you'll see it right there- if you have the car running with the a/c on and hood up, you'll hear the leak (if it is in fact a faulty valve).

 

If you don't already have an idea of what the part is....

http://www.ecklers.com/product.asp?p...8&dept_id=1183

 

I'd also consider the programmer. This has the vacuum 'octopus' attached to it and is located up under the drivers side dash. One of the symptoms of this controller failing is the inability to change vent outputs.

 

The problem isn't the cost but getting the old programmer out and the new one in. It was the most difficult job so far for me.

 

Of course it would have to be difficult. The reasons why I hate having a driveway without a garage.

 

The programmer on my 88 just had a bunch of bad solder joints, keeping all vent f(x)'s from working, and I was able to resolder them w/o purchasing a new one.

 

his price was $289 ! back in 96 they had some trouble with the programers,so the one i have now is the new updated version of the programer.there is a guy in fla,that has some his price is $575 plus del.
i don't known if it is the updated one.

 

I got a better deal on my car because I thought the AC was Fd up. Turned out to be a $6 part The heat just destroyed the plastic and it fell apart. When I brought the remains into the parts counter the guy didn't even ask what it was and pulled out a new one. Said every Chevy with AC & cruise have this issue. I'm willing to bet your cruise doesn't work either

 

I'd check the vacuum valve first! It may only cost you 6 bucks....When it failed on my '95, the a/c also only blew out of the windshield and floor vents, but it was only the valve.

Oh yeah - my cruise control didn't work either....

 

 

First, all automotive HVAC's use vacuum to control where the air flows and GM's strategy is to suck the Defroster door shut as well as open meaning that the source is always doing something - even with HVAC off. When it loses the source, gravity takes over and the Defrost door simply flops open.

Source begins somewhere on the intake plenum and goes through a checkvalve so that it only sucks in one direction. For low vacuum situations, a tank is used for storage. On the Vette, that's usually in the left headlight well. This vacuum is also shared with Cruise (for those models that don't have electronic Cruise and none of the C4's do). Troubleshooting should start at the source which you can follow to the Checkvalve. You would also want to check the tank if there's an "on/off" condition. Pump it up with a vacuum pump and make sure it holds.

How the vacuum gets to the solenoids that work the HVAC doors varies somewhat by Year and whether or not it's an Electronic or Manual unit. Manual units simply direct vacuum by turning a **** or pushing a lever that allows it to flow to the correct solenoid. Electronic units shift the source, well electronically through a processor called a Programmer. Early units (through '89) aren't terribly sophisticated and really don't process a whole lot. After that, GM increased the computing capability of the Unit and added a BCM and PCM interface for compressor control and troubleshooting (though none of the trouble codes will diagnose a vacuum problem). Anyway, if your Vette has an electronic unit and if you've verified the source vacuum in the engine compartment, you've got to make sure it's reaching the Programmer at the Programmer. If it is, then there's a good chance that the Programmer isn't working. Note - BCM linked Programmers can be diagnosed with a Bi-directional scanner with the right cartridge. The Scanner will emulate the dash signals - sent digitally over a serial data line for these models - and if it works, that will tell you that the serial data line is fubar or the Dash Controls are bad. That might be something to consider if you have a '96. That Programmer is unique to that Year and the last price I saw for a new one was about $600. HOWEVER, there have been multiple posts about a poor vacuum harness connection at the Programmer causing these symptoms for this Year, so you might try a Search (since Tech Tips is broken?) if you have a '96.

Individual solenoids use to fail with some regularity - like back in the '70's, but they no longer seem to be a problem. If you suspect that one isn't working - you find vacuum at the solenoid and the door isn't moving - you can check them out with a hand held pump. GM likes to color code solenoid vacuum hoses usually using PINK for Defrost, BLUE for the a/c vents, RED for heat and ORANGE for outside air.

 

Is the 96 suppose to have that check valve? My cruise does not work and i have had problems with ac blowing out different vents at times. I purchased a check valve yesterday and when i got home i found that my 96 did not have one. It had a three way line installed. I installed the check valve but it did not fix the cruise control issue.

 

The picture I posted of it above on on the passenger side under the plastic cover. Mine is a 94 LT1 so I imagine yours would be the same unless it's an LT4??