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.
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.