Chevy Astro and GMC Safari Forum banner

How to fix No Air from Vent / Vacuum / Intermittent AC Issue

147K views 292 replies 149 participants last post by  AstroWill 
#1 · (Edited by Moderator)
I have been having the "defrost only" or "No air flow through my vents" / "Intermittent AC" problem and have been researching all over for a solution. A lot of posts have pointed to the problem and alluded to the solution but the question which like most persons I have been asking is how do I fix it. So I just fixed the issue on my 2000 Safari and I thought I would document the solution.


Tools Needed:

- stubby (2 inch) flat head screw driver or socket/ratchet handle

- a friend with a small hand

- bright enough work light

- 2 beers if you are alone, and 2 for each friend who decides to help. (You will need these).


Parts Needed

GM Part Number - 15967970

I bought the part for CDN $10.90 in Edmonton, Alberta

Here is a picture of the part


Here is the GM Tear down for this part. The one you are interested in is #12 .


Step 1 - Identify that this is your problem part.

Find the vacuum and trace it. If its not obviously broken, trace it to the end and look for cracks on it. It runs from behind the the silver AC tank and on the right of the heater core on the passenger side under the hood. Mine looked fine at first, but as I traced my hand over, about half way down it just disintegrated. Click on any of the following thumbnails for a more detailed pic.





Step 2 - Remove essential parts in the path

If you have determined that this part is bad, removed the air cleaner box and the hose going to the intake manifold. There is a metal piece to which the intake rubber hose connects, you can move it too. It will give you about 1 additional inch of work room (every inch counts! trust me). I didnt move this metal but in retrospect it prolly would have saved me 20 minutes or so.




Step 3 - Remove the old connection from the back of the engine

This part can be tough, and if you have long skinny arms, or if you have a friend with this tenet, then you are in luck! This end is on a little valve on the back of the engine about even with the gas pedal on the driver's side. In case your existing vacuum line broke off and you are not sure where to look, just take a good look at what the end should look like as per the first pic in this post, then look at the pic below for the routing. In a dark skinny hole (hence the need for the bright worklight) on the back of the engine you will see two valves.. one points up and just above that is another which points frontwards and slightly left . The latter is the one you want. You will probably only be able use your index and middle finger. Pull hard on the connector and it will come off. When you get it off, have a beer on me!



Step 4 - Putting it back together again

Be strongly advised... Start by connecting one end of the new vacuum hose to the connector described in step 3 . You want the upper side free because if you have arms like mine, then you wont be able to see in the dungeon properly as your hand will be in the way. So place one end of the vacuum hose between your index and middle fingers on the right hand, take a good look at where the connecting valve in, then lean forward and try to reconnect it. This is the hardest part.. but dont give up. You may even be tempted to go pull the doghouse.. this will not help! When it snaps on, force it on, remove your hand and verify. If its not on completely, go ahead and force it on. When its all done, have the second beer on me. So when this end is properly connected, I suggest routing the other end above the radiator hose, and above the intake manifold, and then to the T-connector at the top. Then reassemble your intake manifold and air cleaner box.


Without taking off the doghouse cover, project should take about 30 - 45 minutes.


Now, go enjoy the whiff of air from your vents as if your truck was still new.
 
See less See more
9
#227 ·
Rookie162 said:
How do i fix that now?
LOL, see the can of worms you opened?

These things are addictive. If you really want to dig in it might be worthwhile for you to get a FSM, factory service manual otherwise just hang out here and all will be explained.
The tool Kenny is talking about needs a picture, a description will just confuse you.

Kenny,,,,,

:angry-tappingfoot:
 
#228 ·
WoodButcher said:
The tool Kenny is talking about needs a picture, a description will just confuse you.
Kenny??? who dat???

Here's an example of the tool. It has different views. Note the jaws on the piece at the end of the cable. The jaws attach to the hose clamp jaws. Squeeze the handle and it ratchets the hose clamp jaws open and holds them open.

Don't know about the price.

Got mine at Princess Auto in Canada.

http://www.banggood.com/630mm-Remot...el-Oil-Water-Hose-Removal-Tool-p-1026764.html
 
#229 ·
WoodButcher said:
just hang out here and all will be explained.
Some people got nothin' better to do with their time. :lol:

I stripped my entire vacuum system down including the dash with all the actuators. I got at the heater recirc unit when I had the AC evaporator out. I know how frustrating it can be tracking down the hoses and all. Figured it was easier to explain it once and for all.

I've actually got heat now.

BTW...did you read my post where I confessed to forgetting to reconnect a hose clamp on one recirc unit hose and the hose popped off on me in the middle of nowhere? I was up to my elbows trying to get long nosed vice grips onto the hose clamp to slide it back on while watching for bears sneaking up on me.

First thing I did when getting to civilization was go to NAPA for hose clamp pliers. They did not have the type I wanted and sent me to Princess Auto.
 
#231 ·
Rookie162 said:
I think im bringing the van to the dealer on that note.....sounds too intricate me for with my big hands
The problem there, as you know, is the problem I described may not be the problem. I responded to another post that the water recirc unit is under the hood by the water bottles. That was the problem with my lack of heat from the heater.

If you get an unscrupulous dealer they could run up the bill pretty fast.

It's not as bad as it sounds, depending on your tolerance level. My mitts are over-sized as well and I had little problem accessing everything once I had a good look at it. It's more tedious, getting at the various bolts and hoses.

I did not need the special tool when I did the work at home. I was able to remove the recirc valve enough to access the 4 hose clips with long nose vice grips. I bought it mainly for emergencies on the road and also to access the larger hose clamps on the main water hoses from the radiator. They are really hard to get at with vice grips.
 
#232 ·
Rookie162 said:
I will say that my REAR HEAT is on high and the vent directly behind me in the middle back bench foot area is blowing cold....while the rear vents over the back doors arent blowing any ar at all.....now to figure this out. Any ideas?
First off, lets take care of something up front...
The newest of these vans in the entire world is 11 years old, so our vans need to be worked on, and getting someone to work on them is expensive. Therefore, if you want to keep the van and not spend a fortune like I did at first, you need to learn the basics and do them yourself. This is a perfect opportunity.

Learn to remove the doghouse. You will need to do this to accomplish many tasks, like replacing the vacuum lines. Its daunting at first but do it once and you will be a pro there after. I used this video to learn the process:
Remember, I was a rookie like you here only ONE tiny little year ago, but I read a lot and learned from the good folks here... and by not being intimidated by it all.

Now, to your specific questions...

Rear vents over the back doors are for rear AC only, not heat, so you're good there.

You need to replace ALLthe vacuum lines under the hood since that valve is vacuum operated and you might not have enough vacuum to pull it and the vents. It could also be stuck like explained above. These valves like to disintegrate so if it hasn't been replaced yet, might wanna go ahead and do it before it breaks on its own and strands you like it did to me... on 2 different vans. The tool referenced above is a must have for these @#$% squeezy clamps, get one, they are cheap.
I believe this is the replacement part you are looking for (also available at your LAPS)
Link: http://a.co/fq8D7HA

Replacement isn't too bad. Remove the upper fan shroud to get to it (leave the bottom one alone or god will punish you). Then mark the hoses or take a picture of it all like suggested above and the rest is easy. I did it on the side of the road once in 105deg heat and with a few very basic hand tools, took about an hour.

Keep at it and don't let it intimidate you. Please post your progress so we can follow along at home.

WELCOME TO THE FORUM!

-Wimpy
 
#233 ·
Wimpazz said:
Rookie162 said:
I will say that my REAR HEAT is on high and the vent directly behind me in the middle back bench foot area is blowing cold....while the rear vents over the back doors arent blowing any ar at all.....now to figure this out. Any ideas?
First off, lets take care of something up front...
The newest of these vans in the entire world is 11 years old, so our vans need to be worked on, and getting someone to work on them is expensive. Therefore, if you want to keep the van and not spend a fortune like I did at first, you need to learn the basics and do them yourself. This is a perfect opportunity.

Learn to remove the doghouse. You will need to do this to accomplish many tasks, like replacing the vacuum lines. Its daunting at first but do it once and you will be a pro there after. I used this video to learn the process:
Remember, I was a rookie like you here only ONE tiny little year ago, but I read a lot and learned from the good folks here... and by not being intimidated by it all.

Now, to your specific questions...

Rear vents over the back doors are for rear AC only, not heat, so you're good there.

You need to replace ALLthe vacuum lines under the hood since that valve is vacuum operated and you might not have enough vacuum to pull it and the vents. It could also be stuck like explained above. These valves like to disintegrate so if it hasn't been replaced yet, might wanna go ahead and do it before it breaks on its own and strands you like it did to me... on 2 different vans. The tool referenced above is a must have for these @#$% squeezy clamps, get one, they are cheap.
I believe this is the replacement part you are looking for (also available at your LAPS)
Link: http://a.co/fq8D7HA

Replacement isn't too bad. Remove the upper fan shroud to get to it (leave the bottom one alone or god will punish you). Then mark the hoses or take a picture of it all like suggested above and the rest is easy. I did it on the side of the road once in 105deg heat and with a few very basic hand tools, took about an hour.

Keep at it and don't let it intimidate you. Please post your progress so we can follow along at home.

WELCOME TO THE FORUM!

-Wimpy
I think ill go for it bud!

Thanks for words of encouragement
 
#235 ·
Rookie162 said:
I think ill go for it bud!
Good deal.

About your long quotes, hit the 'quote' button at the top of the post to reply. Highlight just the text you want to quote and hit the tab at the top of the edit window named Quote. It will add special brackets to the front and end of the quote so your selected text will be highlighted in a window in the reply. Repeat for each section of text you want to quote.

You may have to delete the text you don't want. I just copy/paste the brackets stuff that's already there after you hit the quote tab to reply and delete what I don't want.

For URLs, copy/paste the URL to your reply, highlight the URL by dragging your mouse over it, and hit the URL tab at the top of the edit page. It will add brackets around the highlighted URL so it's active in your reply.

You can use the preview feature to check for accuracy with your quotes.

That way readers know what you are talking about without the entire post being re-posted.

I don't use a lot of the features available and maybe someone who does could add more info.
 
#237 ·
I had the same problem of the fan not working on high and not blowing out of the front of the dash. This post helped tremendously. I had everything taken apart to remove the factory stereo. I immediately found the culprit vacuum hose as described...most of it was missing. I got a replacement for like $5, plus replaced all the other small vacuum lines. The weird thing is there was one coming out of the side of the valve that the broken one plugs into that went to nothing :? See pic. After I got everything put back together I was stoked because the stereo all worked and sounded great....but the vacuum problems still persisted. Hmmm. Being the slow genius that I am I went and put a screw in the "hose to nowhere" and what do you know? It all worked! Does anyone have info on what that hose/line is supposed to go to? Vacuum ball?

 
#239 ·
I searched high and low for a vacuum ball. Couldn't find one. The screw works...eh that is before I put it in, no Hi setting for the fan and no air through the front vents, as others in this thread have described exact same problem. But with the screw in there they work. However on lower than Hi setting from time to time it sounds like there is probably a hamster going around and around on a hamster wheel.
 
#241 ·
Oh yeah, I replaced those too. But I was going to post about that on the other thread. As well as the window motor driver side. The only problem that remains with the fan/air is the sound from the dash on occasion. Kinda sounds like a little trap door opening and closing lightly.
 
#246 ·
Broseph said:
The only problem that remains with the fan/air is the sound from the dash on occasion. Kinda sounds like a little trap door opening and closing lightly.
That's not a problem, it shows the system is working. There are trap doors operated by vacuum actuators. The trap doors do things like diverting air to the defroster vent, the floor heat vent, or both. Another diverts air from the outside. Another diverts warm air from the heater.

On my 2001 Safari, I had an issue where a door was colliding with another door and it could be rather noisy. I pulled it apart and re-aligned the doors. I don't recommend that unless it's absolutely necessary since it involves pulling apart a large amount of the dash.

If the trap door sound is fairly quiet, it should be OK.
 
#247 ·
After excruciating days chasing & replacing vacuum lines, looking under the dash etc. I finally replaced the check valve that runs from the vacuum canister reservoir. The check valve uses the reservoir & keeps vacuum in the system during acceleration / wide open throttle.

AC Delco.jpg
It is Vacuum Check Valve GM# 271

Dorman.jpg
Don't use the Dorman equivalent, it literally sucks does not seal as good !

valve.JPG
The hose on black part draws from the engine vacuum port, the split goes one each to the a. ball reservoir & b. controls under the dash.

Finally I use red (or any color) 3mm (1/8") Red Silicone Vacuum Hose spliced in to/or replace the hard plastic or rubber lines as needed.
600.jpg
It stretches quite a bit and will hold tight on a variety of nipples.The color really stands out and helps me keep track of the lines.
 
#248 ·
The engine needs to be running to operate the vents, correct?[/quote]

Basically yes........the vents will work for a short period of time (2--3mins) after the engine is stopped because the vacuum will bleed-off as the vacuum system is not 100% sealed.

You hit the nail on the head Steve.......Dorman check valves suck. Get AC Delco (GM) original replacement # 15-5068 only.

Second thing that you did was excellent.......use a colored vacuum hose replacement so it's easy to see where it goes in all that dark engine area. I got three different silicone hoses. Yellow, blue and red. What a difference !!

steve93101 said:
After excruciating days chasing & replacing vacuum lines, looking under the dash etc. I finally replaced the check valve that runs from the vacuum canister reservoir. The check valve uses the reservoir & keeps vacuum in the system during acceleration / wide open throttle.

It is Vacuum Check Valve GM# 15-50568

Don't use the Dorman equivalent, it literally sucks does not seal as good !

Finally I use red (or any color) 3mm (1/8") Red Silicone Vacuum Hose spliced in to/or replace the hard plastic or rubber lines as needed.
600.jpg
It stretches quite a bit and will hold tight on a variety of nipples.The color really stands out and helps me keep track of the lines.

Leeann_93 said:
Jack up passenger side front. Pull wheel well liner. See this:



That round thing is the vacuum ball.
No need to pull the wheel....just turn it all the way to the right and remove front section of the mud flap by pulling the plastic pins that hold it in place. Right there in your face !! No jacking up the van or wheel removal needed.

Mike Cecchini
Bethesda, Md.
 
#251 ·
Why? Use a box cutter, cut on the lines. Takes under 5 mins.

When you install the new blower motor, put the piece of plastic you cut out back over the blower motor. All is well.

Oh, replace the blower motor resistor at the same time. Dunno which is the chicken or the egg, but one failing tends to bring down the other. You will need a 5.5mm socket or nutdriver.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top