View Full Version : dash vents not blowing air??


bigti99a
05-10-2008, 11:48 AM
ok on my way in to work today i go to hit the a/c. i hear the fan blowing and dont feel anything coming from any of the vents. there is cold air flowing b/c i feel it at my feet and at the defroster. i turned on the warm air and the same thing.
the derfroster and feet vents work fine. it is the 4 dash vents that are not working. anyone ever heard of this? could there be something jamming teh vent system?
HELP!:bang:

2001NBMZ28
05-10-2008, 04:14 PM
Blowing only at your feet/defroster is the default setting - you've got a vacuum leak. Check for a loose, cracked or disconnected vacuum line behind the intake and going towards the passenger side.

bigti99a
05-10-2008, 04:23 PM
ok i will check when i get home. i did degrease the engine with simple green last weekend. no problems noticed other than this. can they be related?

bigti99a
05-13-2008, 10:06 AM
alright i check real good for any cracked hoses this morn. i did not see any so i fired the car up and turned on the dash vents. still nothing, not that i expected it to magically fix itself. but i felt around both sides and behind the intake manifold to see if i could feel anything. there is a valve on the air system on the drives side that was putting out some air then stopped. i doubt the air system has anything to do with this issue.
can somebody help narrow my search for a leak or other cause to this? HELP!! i need to get all the BS things taken care of before summer gets in full swing!

zaner
05-13-2008, 10:13 AM
To the right of your pcm is a black check valve canister that has 2 or 3 vacuum lines coming off of it. Id say the valve is no bigger than 1 1/2" x 3/4". Mine randonly started doing the same symptoms of yours and thats where I found the vacuum leak at.........

bigti99a
05-13-2008, 10:41 AM
should i run the car while i am checking it? will spraying any soapy water help show it as well? and am i hurting anything by driving it? thanks for your help.

bigti99a
05-13-2008, 10:53 AM
ok i checked there and have found a very tough plastic line has be shredded. i cant seem to fine the other end. on that valve there is one line on one end and two on the other. the problem line is the straight line off the side with 2 lines on it. it looks like the run into the wire protectors around the pcm. can anyone tell me where this line is supposed to go so i can find the other end. and to i just need to find a way to join the 2 or should the whole thing be replaced?
....and a million thanks to everyone that has ever helped me on this board. i am a car lover but not a guru mechanic. Zaner your input has saved me tons of time!!

Phoenix 5.7
05-13-2008, 10:59 AM
if i had to guess, its the tiny black hard plastic line that goes to the back passenger side of ur intake manifold. i had mine come off and it did the same thing, and that line feeds the vacume for that little black valve thing

1sick'98WS6
05-13-2008, 03:17 PM
if i had to guess, its the tiny black hard plastic line that goes to the back passenger side of ur intake manifold. i had mine come off and it did the same thing, and that line feeds the vacume for that little black valve thing

Correct, it goes into a little rubber sleeve right by the map sensor

bigti99a
05-13-2008, 05:20 PM
will driving like this hurt anything until i put my ls6 intake on in the next week or so? and where do i get a replacement line, or coupler?

2001NBMZ28
05-13-2008, 09:07 PM
Won't hurt to drive it, parts are probably a dealer item.

my2kTA
08-09-2008, 09:16 PM
just wanted to say that I found this thread while trying to figure out why my top vents werent blowing since I had the engine built up. This was very helpful as i checked the little valve and followed one of the lines to an emty connection. i had the GF check the back of the intake since she has small hands and viola...1 minute later i had cold air blowing out of the vents again :D

this was the only thing keeping me from driving my car as much as id like and i was getting ready to take it to an AC specialist :X

Mr. Trick
08-13-2008, 01:08 PM
I'm having the same issue right now. I havent checked behind the intake, but the plastic line that goes in the wire loom was disconnected. It looks like it goes around to the driver side, what is it supposed to be connected to?

my2kTA
08-13-2008, 05:25 PM
I'm having the same issue right now. I havent checked behind the intake, but the plastic line that goes in the wire loom was disconnected. It looks like it goes around to the driver side, what is it supposed to be connected to?

If i am thinking straight, this is the same one that I had disconnected.

The little valve has 3 connections. On mine the top connection runs down to the horn (pass headlight area) the bottom one goes to the back of the intake (towards the driver side) and the back one seems like it heads back to the firewall.

t/afrom504
08-17-2008, 05:14 AM
what size is that line that goes to the firewall anyway? when i checked the line at the firewall, i felt a hole in it...

HoLLo
08-18-2008, 09:55 AM
I had a similar problem before, the air only blew on my feet. I had been messing with the harness behind my radio and accidentally had pulled out this little harness with a couple vacuum lines attached to it that ran to the HVAC control knobs. I plugged them back into the HVAC controls and I had working air vents. You could hear a vacuum leak inside the car (almost sounded like radio static though) when the vacuum was unhooked. It was very tight trying to plug the harness back in, but it went. Try that out.

JScamaro
08-20-2008, 02:30 PM
I had this same problem when I removed my AIR equipment. I acidentally pulled out that tiny vacuum line behind the intake.

You could hear the AC blowing but nothing coming out of the vents. I would say the line felt even smaller than a straw since I couldn't really see back there.

I had to go one day in the Texas heat without AC and it definitely sucked.

yeller_xtc
08-20-2008, 07:11 PM
pull the knob off your selector switch make sure it isnt broke. thats what was wrong with mine...if thats the case ill send you a spare knob..

spdrcr7882
05-12-2009, 12:46 AM
I had the same problem, found the black hose that goes to the back of the manifold, sure enough it was disconnected. I hooked it back up and sure enough, now my vents work for my a/c.
thanks for everyone's help.
justin

cnw8891
05-25-2009, 04:21 PM
Does anybody have a part number for that check valve? My junk broke and this Georgia heat is a force to be reckoned with.

mike171562
03-29-2010, 04:49 PM
I believe its GM Part# 14056648, i got 5 in a bag at Advanced Auto today for 1.98

SlayerMaro
03-29-2010, 11:26 PM
Did you guys experience other issues associated with vac leaks while you had this one?

My top A/C vents don't work, and I also have the idle issues associated with a vac leak. Just wondering if that could be the cause.

cnw8891
03-30-2010, 12:33 AM
I believe its GM Part# 14056648, i got 5 in a bag at Advanced Auto today for 1.98

Thanks. But after having 3 or 4 more of the GM check valves split, I rigged my own with a regular check valve and a t-fitting. I've had no problems since.

Did you guys experience other issues associated with vac leaks while you had this one?

My top A/C vents don't work, and I also have the idle issues associated with a vac leak. Just wondering if that could be the cause.

I had no other vacuum issues.

Elthesh
04-01-2010, 09:52 PM
For what it's worth... My 10 year old check valve just died and i replaced it with the Dorman version of that part. Works great now. Too bad I missed it on the first check and bought a new switch for inside. Man, that switch is a major pain to replace. but at least its shiny new now. The check valve was split along the line where it molds together along with a huge split lengthwise. Easy quick repair though.

Dan
04-04-2010, 09:13 PM
Mine did this a few years ago when I put on the LS6 intake(98 T/A)..The hose on the back came off & I tackled it today after 6 years:D..Well I had to pull the intake to hook it back up. No dice, still no air thru the vents. I tried both T splitters,(one from my 99 T/A) So I don't know what the hell is going on. I know the T Splitter on my 99 is working but honestly not all the time. I would put the air on & for a minute it would stop blowing out the vents & then start again. maybe I just need to start fresh with 2 new T splitters & see what happens. I busted my balls taking off that intake today thinking this would fix it:bang:

bluebird71
06-18-2010, 08:57 PM
I found the little black hard vacuum line behind the manifold and it's off on mine too. Problem is, I can't get it back on there for the life of me. It feels like it's the same size as the nipple it plugs into. I no longer have any EGR stuff and I had a FAST intake on it before the turbo build. Do I need some kind of connector that steps the nipple down or something?

fleetmgr
06-18-2010, 09:12 PM
can you make a splice from a piece of vacuum hose?

bluebird71
06-18-2010, 11:12 PM
Ok, nevermind, I got it connected and it worked. The AC and upper vents now work. I also had to replace the compresser fuse as well.

desormeaux05
03-21-2012, 06:06 PM
Where exactly does the vacuum line go on the back of the intake manifold? I just can't seem to find a nipple there for the life of me.

KrisXpc
03-22-2012, 04:13 PM
Where can i find the vacuum line connection for the vents? Is it on the Hvac box? I know where the connection is on the intake, just not for the vents. Had the engine removed and engine bay painted i doubt that the painter ever hooked it back up.

mike171562
03-22-2012, 04:58 PM
Where exactly does the vacuum line go on the back of the intake manifold? I just can't seem to find a nipple there for the life of me.



http://i112.photobucket.com/albums/n186/mike171562/ops48.jpg

KrisXpc
03-22-2012, 06:04 PM
I want a pretty picture with labels answering my question too =[

djfury05
03-22-2012, 09:33 PM
There should be a vacuum line coming out of the HVAC box to the left of the heater hoses at the top. This is the line that all the other vacuum lines connect to with the T fitting. One line of the T fitting goes to the back of the intake as shown above. The other line runs down the passenger side and into a vacuum canister under the frame fail near where the horns are. Are you saying you don't have the line coming out of the firewall anymore?

KrisXpc
03-23-2012, 09:15 PM
There should be a vacuum line coming out of the HVAC box to the left of the heater hoses at the top. This is the line that all the other vacuum lines connect to with the T fitting. One line of the T fitting goes to the back of the intake as shown above. The other line runs down the passenger side and into a vacuum canister under the frame fail near where the horns are. Are you saying you don't have the line coming out of the firewall anymore?


You Rock man.. I had the nipple at the firewall but no actual lines.. First time in 4 years the vents have actually worked.. Since i only have heat in the car and i dont drive it often it's not been a huge worry..

sxemama
04-10-2012, 01:58 AM
I'm having the same problems. Just comes out the defrost vent. I know nothing about where these things are located, so how exactly do i access whatever i need to check?