A/C coming thru defrost - the final answer.
Thread Starter
Instructor
Joined: May 2005
Posts: 182
Likes: 0
From: Glendale AZ
A/C coming thru defrost - the final answer.
91 L98 convertible vette.
I have researched through this site the many fragmented topics of air box control failure resulting in AC coming from defrost. I have a couple questions.
#1 - the vaccum line that connects to the harness on the firewall behind the distributor has been broken off. Is this indeed the feed for vaccum for the manifold to control the air box?
#2 - is there a manual way to lock the blend air door in the air box to always come from the vents? I live in AZ, and defrost really isnt ever a problem for me. I would like a quick fix until i can get the harness replaced if it is indeed the issue.
Thanks.
I have researched through this site the many fragmented topics of air box control failure resulting in AC coming from defrost. I have a couple questions.
#1 - the vaccum line that connects to the harness on the firewall behind the distributor has been broken off. Is this indeed the feed for vaccum for the manifold to control the air box?
#2 - is there a manual way to lock the blend air door in the air box to always come from the vents? I live in AZ, and defrost really isnt ever a problem for me. I would like a quick fix until i can get the harness replaced if it is indeed the issue.
Thanks.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
What you describe should be the vacuum line to the a/c programmer (electronic air) or dash controls (manual air). To prevent performance problems, I'd plug it up. Otherwise, patch it with some rubber line that's close and your a/c will probably work normally. If you want to fix the door positions you need to get the top of the dash off to access the defroster box and door - possibly more to access the heater doors which are inside the heater plenum below it. The defroster door is going to be problematic because gravity is keeping it open so it will be up to your own ingenuity has to how to keep it permanently closed.
Le Mans Master
Joined: Jul 2001
Posts: 8,184
Likes: 3
From: Santa Maria, CA
Originally Posted by sremenap
91 L98 convertible vette.
#1 - the vaccum line that connects to the harness on the firewall behind the distributor has been broken off. Is this indeed the feed for vaccum for the manifold to control the air box?
#1 - the vaccum line that connects to the harness on the firewall behind the distributor has been broken off. Is this indeed the feed for vaccum for the manifold to control the air box?
That tubing is old and brittle by now. You could pull the old stuff completely out and replace with new stuff.
I would like a quick fix until i can get the harness replaced if it is indeed the issue.
It will probably make your system work normally and give you full control again. "Replacing the harness" would not include the tubing, only wiring from the ECM to the engine, so that's probably not what you want. The vac tube feeds this controller:
It is housed in a black plastic box bolted to the interior firewall next to the steering column.
Last edited by pablocruise; Jun 21, 2005 at 01:55 AM.
Le Mans Master
Joined: Dec 2000
Posts: 7,839
Likes: 22
From: San Diego, Ca
The Discounters usually have an array of vacuum line accessories along with the glue (though I usually just use super glue). I'd take the Programmer off, measure the hole and then go shopping. Should be able to mickey mouse something that works.
Pro
Joined: Jan 2005
Posts: 686
Likes: 62
From: San Jose Ca
Originally Posted by sremenap
Well my problem is that the nipple for the vaccuum line seems to have been broken off
Any ideas?
Any ideas?
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Drifting
Joined: Mar 2002
Posts: 1,251
Likes: 2
From: Thomson Georgia
89 Paul in Cal and MaxLean have both got it right.
More often than not, you'll find the plastic vac line has broken.
It usueally happens during a distributor or the cap has been changed, or the manifold has been taken off.
More often than not, you'll find the plastic vac line has broken.
It usueally happens during a distributor or the cap has been changed, or the manifold has been taken off.
Thread Starter
Instructor
Joined: May 2005
Posts: 182
Likes: 0
From: Glendale AZ
Originally Posted by MaxLean
Where is the broken nipple in that pic? If you're refering to the circular item to the left of the wire bundle, that's something else and not related to the vacuum supply to the HVAC.
Burning Brakes
Joined: Apr 2004
Posts: 859
Likes: 7
From: Spring Texas
St. Jude Donor '05
Mine did the same thing after a installing a new intake - turned out to be a vacuum line that connected to the intake was not on - hooked it back up and everything worked fine..
Burning Brakes
Joined: Aug 2002
Posts: 926
Likes: 2
From: chandler az
At the bottom just right of the middle of the picture - see the brown connector? just to the right of it is the vacuum connector. it goes into the wire loom that exits the top of the picture.
Thread Starter
Instructor
Joined: May 2005
Posts: 182
Likes: 0
From: Glendale AZ
yeah - thats what i thought was teh vac line - but where is that wire harness. where does it originate? I cannot tell from the pic, and stared my engine compartment over to try to find it.
Drifting
Joined: Mar 2002
Posts: 1,251
Likes: 2
From: Thomson Georgia
It's between the rear manifold flange, where the distributor goes, and the firewall. This wire bundle contains the wiring going to the dash, the computer and such. Right where the AC box bolts to the firewall. If it's broken all you will see is the stub of the plastic hose sticking out of the bundle.
It's a whole lot easier to get to and to see if you take the distributor out.
It's a whole lot easier to get to and to see if you take the distributor out.
