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HVAC Vacuum Hose location on 1989??

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Old 02-13-2018, 09:07 AM   #1
tbone777
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Default HVAC Vacuum Hose location on 1989??

Just purchased my first corvette and the vacuum lines were missing and and dry rotted. I have all the vacuum lines replaced except for one, the HVAC line that goes from the check valve to the firewall. It is nowhere to be found, so my question is where does the line exit the firewall? Is it behind the distributor, on the driver or passenger side, near another wiring harness? I can't find it anywhere? 1989.
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Old 02-13-2018, 09:40 AM   #2
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Follow the ECM harness up to the 'pass through' at the firewall. Vacuum source should become obvious. Under-hood it's behind/near the distributor. An easy find. In this thread there's snapshots of the 'pass through'. I believe I've linked to #8 but look at #12 and #14 also.

Do you have the FSM(Factory Service Manual)?

https://www.corvetteforum.com/forums...post1586480882
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Old 02-13-2018, 09:59 AM   #3
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I followed the ECM harness that exits on the drivers side firewall near the battery. For some reason that bundle of wires doesn't have any vacuum lines. I guess the next step is to look at the ECM wiring inside the car above the brake pedal and see if the vacuum line can be found.
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Old 02-13-2018, 10:05 AM   #4
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Quote:
Originally Posted by tbone777 View Post
I followed the ECM harness that exits on the drivers side firewall near the battery. For some reason that bundle of wires doesn't have any vacuum lines. I guess the next step is to look at the ECM wiring inside the car above the brake pedal and see if the vacuum line can be found.

left side of car behind/near battery is C100 and there's NO VACUUM there, all electrical. The snapshots in the link should make it very easy for you to see where you need to be. Sounds as if you need a FSM.

Here's an image of 'inside the car' - where this image says S135/S152 is the 'pass through'.

Name:  L98 pass through.jpg
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Old 02-13-2018, 10:16 AM   #5
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Ok Thanks! I will look in that firewall location to see if I can find it. Yes, I do need a FSM, hope to find a cheap one on eBay.
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Old 02-13-2018, 02:15 PM   #6
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Here is a pic of the S135 connector on the engine side of the firewall. Maybe I'm just not seeing it. I searched through this wire bundle and didn't see a vacuum hose.

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Old 02-13-2018, 06:02 PM   #7
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It will NOT be a hose but likely only a 7/32 -1/8" hard tube. I mentioned following the harness up from inside the car and I still think that's likely easier to determine if it's actually still there.

I have an '89 C68 harness here and if you put your hands on the ECM connectors in the car the connector(vacuum 2 port white) in that #8 post is obvious. It's taped to the outside of the ECM harness. I ain't unwrapping mine but you should have no issues.

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Old 02-13-2018, 08:21 PM   #8
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as a matter of fact I just did this exact thing on my 86 last night. Chances are you will find it closer to where it is located in my picture. It gets broken off during removal of the distributor. You do not need to pull apart the harness as far back as I did or it looks like as far as you did either. Using my photograph here you can see where it pokes out of the harness. Buy yourself some small rubber vacuum line and it will fit right over top of the small nipple that is sticking out from the broken part.

that's what I did and it works great.

https://www.corvetteforum.com/forums/c4-tech-performance/3909126-restoring-a-1986-manual-4-3-z31-pics-9.html#post1596578045
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Old 02-13-2018, 08:28 PM   #9
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Let's see if my link works better than yours!!

https://www.corvetteforum.com/forums...post1596578045
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Old 02-13-2018, 09:27 PM   #10
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doh! thnx!
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Old 02-16-2018, 09:28 PM   #11
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I finally located the hvac vacuum hose. I went back and looked through the bundle of wires exiting the firewall and it was hiding right behind the distributor base, and of course had broken off at the 90 degree turn. Thanks for everyone's help!!!
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