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ac blowing out the defroster instead of dash


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jackx
User

Aug 16, 2015, 5:22 AM

Post #1 of 9 (1671 views)
ac blowing out the defroster instead of dash Sign In

I have a 1989 Jimmy s15 4.3 . It only blows cold air out the top where the defroster vents are.
I pulled out the ac controls that the blower switch is attached to. On the back is where all the
vacuum hoses are attached. It looks ok and still has the fasteners on it to hold the hose attachment
plug on. The plug has all the hoses hooked to it. The plug just snaps onto the vacuum nipples attachment.

Ever so often it will get enough vacuum for the air to start coming out the mid dash vents but
that happens very rarely now.

Where does the vacuum line that supplies the vacuum to the controls run to? I'm thinking maybe
there is a break in the vacuum line somewhere but I don't know which color of vacuum line is the
line or where it connects to the vacuum reservoir if it has a reservoir.

I also noticed that when you switch the ac switch from AC to Max (which recirculates air in the truck that has
allready been cooled) nothing happens. I don't hear
any doors open and the air flow does not change. I figured that the lack of vacuum may be responsible
for this problem top. It has a new blow and blower speed control/ Resister.

Any help to get this fixed would be appreciated. Thanks.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Aug 16, 2015, 5:56 AM

Post #2 of 9 (1666 views)
Re: ac blowing out the defroster instead of dash Sign In

I think this does vacuum control ducts and where air comes out via vacuum - default would be defrost ducts. Somewhat common with ones that do is a line under the hood probably black plastic can look like wire fully breaks or part breaks from the vacuum BALL near sure with these well hidden maybe passenger side even under something? Been ages - sorry. Might also be only reachable from under vehicle - not sure. Small nipple on OE ones can bust off too. Any disruption on those type lines with lots less age they aren't strong.


So - look for one going thru firewall and follow it. If flaw found they can be cut clean with a razor and use windshield washer hose as a splice as needed,


T



jackx
User

Aug 16, 2015, 8:41 AM

Post #3 of 9 (1655 views)
Re: ac blowing out the defroster instead of dash Sign In

Well I went and looked at it. The ball is right there on top. The hose is still on it. Another hose is cut. I check and put my finger over the cut hose and not vacuum is coming out. I put a metal pug in it anyway. I have no idea what it
attaches to. I suspect it attaches to something associated with the vapor cannister. It is a lot longer hose than the one attached to the ball.

I let it run while I cleaned it up with the water hose. Probably took about 15 minutes. Got in and ice cold air
was coming out of the dash vents. When I turn it to max I can hears the doors open too. Weird.

What could be causing this. I'm just guessing but maybe it takes a while for the ball to get full of enough vacuum for the vacuum to get the door to open? Maybe the cut hose I plugged was letting so much vacuum escape it causing it to not have enough vacuum to open the doors or maybe the ball is bad? I hate to replace the ball unless it is bad but its only 15 bucks. What do you think?? After I finish this response I will go out and see if it still works. If so then I guess it was the cut hose.

I really like that old truck. Lots of power. It only got 100k on the motor and tranny, doesn't have to pass emissions tests and its white so its paint is fairly easy to touch up.

Thanks for looking into this for me.

Well I went out and checked and its still blowing out the defroster. I guess plugging the cut hose didn't fox it.


(This post was edited by jackx on Aug 16, 2015, 9:13 AM)


Discretesignals
Ultimate Carjunky / Moderator
Discretesignals profile image

Aug 16, 2015, 9:38 AM

Post #4 of 9 (1648 views)
Re: ac blowing out the defroster instead of dash Sign In

You need the vacuum ball or reservoir. Every time you accelerate it dumps manifold vacuum, and it could blow out the defroster. The ball is also used by cruise control, so it could affect the operation of that without the reservoir.

Sometimes those leaks can be hard to find. Seen some leak from the selector switch and couple where the mode door gets jammed up or the servo mounts break off the case.

Best tool I've seen for finding leaks on those is a smoke machine. If you can get someone or a shop to hook one up to the system, you could find the leak easily. You could also troubleshoot it with a vacuum gauge T'd in and then pinching off hoses in different parts of the system to isolate the leak.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Aug 16, 2015, 9:48 AM)


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Aug 16, 2015, 11:11 AM

Post #5 of 9 (1638 views)
Re: ac blowing out the defroster instead of dash Sign In

Cool! At least you are zooming in on the problem area but not done yet. Find out about that cut hose? There's another end or place it should be and if leaking is now likely the source vacuum for something and affecting the vacuum stored in that ball which is storing vacuum so would go "hiss" even a day later without engine running by a check valve in the line someplace.


Tad more: If as said the vacuum line is like wire it still would use rubber connectors or elbows at places as needed. The "ball" if you follow hose should be picking up vacuum from a low spot on throttle body or intake manifold itself. Metal nipples found with nothing and the hose you found you just need to find where it's not hooked up, broken and put back as intended.


IMO there's never a good reason to leave a vacuum hose just open - never. There are some devices if know exactly why you might want to disconnect a vacuum line to some thing not needed (not much) and plug that hose - screw, bolt, golf tee - what works. You should almost never need or want to do that!


For the moment at least you know your dash control CAN work but think they only get just barely enough vacuum so chase down what and where beginning and solving the mystery hose for a start,


T



jackx
User

Aug 17, 2015, 1:35 PM

Post #6 of 9 (1618 views)
Re: ac blowing out the defroster instead of dash Sign In

That cut hose went to the charcoal cannister. Since its not subject to emissions, I will leave the cut end plugged.
It had no vacuum but I guess maybe it doesn't have vacuum unless it is purging. So, I don't think the cut line is
a issue.

The vacuum line coming through the firewall along with some of the wiring harness hooks up to some
L's with elbows like you said. It eventually hooks up to the back side of the intake.

The ball has one hose and is also hooks up to the intake.

I have found no bad hoses. I believe its time to take it to an ac shop.

I have no idea how to check to see where the vacuum leak is. It's probably the rubber fittings that hook the ducts and the vacuum up to the blower switch on the dashboard. I've pulled the switch out and pushed on the rubber connector and it had no affect on the ducts. On other vehicles with the same problem this will usually cause the air to start coming out the mid dash vents. It didn't happen with this old truck.

This is my first rodeo on removing those hoses on a 1989 Jimmy. I beleive they probably need to be replaced. Maybe someone with the hands the size of my grandson can get to where they hook up under the dash but not me.

I called the Coolair ac place and they said they do work on s15's that old and if it is just a vacuum line they should be able to fix it for under 100 bucks. That is kinda low if they have to remove the dash to get to the vacuum hose hookups
So, we will see. I do have my doubts about her knowing how much work is going to be required to fix it. I did not talk to a tech. I suspect I was talking to a woman who is married to the tech who owns the shop. I hope she is right about the repair cost. I have to get it inspected and then I will take it to them. I am afraid I will be paying them 90 bucks to tell me the it has a vacuum leak and it will cost 200 or 300 dollars for them to fix it because they have to pull the dash apart. I may take the truck down and talk to the tech before I spend the 90 bucks.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Aug 17, 2015, 1:51 PM

Post #7 of 9 (1617 views)
Re: ac blowing out the defroster instead of dash Sign In

Don't just blindly plug off stuff just because YOU think it's emission related and YOU don't need to get checked. One can involve another item that doesn't behave so put things where they belong.


If you can't find the break or damage to line thru firewall you could probably overlay a whole new stretch of line if needed.
Hey, emission rules where you are or not have the charcoal canister and lines in place. It doesn't harm anything and re-burns fuel. Now disabled might just fill up with raw fuel and cause a plain explosion or drip or maybe not.


Hose is dirt cheap. Many people will buy rolls of it and do all of it all at once with a decent older vehicle,


T



jackx
User

Aug 18, 2015, 11:02 AM

Post #8 of 9 (1601 views)
Re: ac blowing out the defroster instead of dash Sign In

After reading your post I decided that the hose under the hood is subject to a lot of heat and
even though it has no obvious breaks I guess it could deteriorate and leak enough to cause my problem. I was
hoping the connections under the dash which are not subject to all that heat might be ok.

Then this morning I replaced all the vacuum hose under the hood as a last ditch effort
to fix it before taking it into a shop.

Guess what it works great now. Thanks for your advice. You saved me some money. You might
have thought I wasn''t listening to you. I was and I'm glad I did.

Now just have to install a new radio I got for it and repaint the bad spots and I'll have the Jimmy
back on the road.


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Aug 18, 2015, 11:30 AM

Post #9 of 9 (1599 views)
Re: ac blowing out the defroster instead of dash Sign In

Sounds like a total win, win. Even at the age the problem to me has been common (assorted makes too) and always under hood not in dash.
My own is just as old and all orig. Another whole type of vehicle. Dang design and mostly love it puts those crackle vacuum hoses all over and worst right where you check trans fluid level and bust it right off if not aware of the stupid location.


If this behave a few times when it would have failed you can rest that you really fixed it and good for you,


T







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