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Unread 11-16-2012, 04:14 PM   #1
NashWheel
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1994 ZJ 
 
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Help with Heating/AC controls (Vacuum type)

I am having a bit of trouble finding the issue here. When I turn my heat on, no matter what vent setting, it will only come through the defrost vent. Has anyone else had this problem? Any pointers or tips? Also does anyone have a vacuum circuit diagram of the heat/ AC controls?

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Unread 11-17-2012, 11:23 AM   #2
NashWheel
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Really!! No one else has had a similar issue?! Do you need more info from me or what?
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Unread 11-17-2012, 11:26 AM   #3
jasarge1
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Quote:
Originally Posted by NashWheel
Really!! No one else has had a similar issue?! Do you need more info from me or what?
I have the same exact problem and sorry no clue how to fix it. And can't find a write up on it either
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Unread 11-17-2012, 12:01 PM   #4
moggie99
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If you have a leak in a vacuum line then the system will default to demister vents. The number one cause of vacuum leaks is where the vacuum line passes through the bulkhead on the passenger side (LHD vehicles).
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Unread 11-24-2012, 11:19 AM   #5
NashWheel
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Well I still haven't figured it out. All the lines seem good passing through the firewall. I'm determined to find the culprit, time for troubleshooting is not easy to find. Does anyone know anything about the strange box underneath the battery? How do I test the vaccuum diaphragm for failure?
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Unread 11-24-2012, 12:19 PM   #6
JasonStebbins
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That strange box is the vacuum reservoir. It stores vacuum for the cruise control and HVAC system operations while the motor is under high load/low vacuum. Check that for leaks.
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Unread 11-29-2012, 07:55 PM   #7
cgcarpenter
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So the box under the battery tray only has one hose attached right? Mines is a little loose... And how well is the box sealed? Could it leak from the side seams?

I am also doing this and trying to figure it out... I'm going to do the bubbles trick tonight hopefully.

Is it also probable that there is a fault behind the controls. I'm thinking about taking apart the dash to see what it looks like behind it..
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Unread 11-29-2012, 09:20 PM   #8
KoreaZJ
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Most of these problems are vacuum leaks under the hood.

One hose on the reservoir. Disconnect the hose, is there vacuum on it? Plug it, see if your heater controls work.


Removing the panel looks something like this 94 pic. Vacuum lines are larger colored in the center. Black vacuum line disappearing into the shadows is the supply line which runs out through the firewall to the tee fitting, then to the vacuum reservoir.




If you need to remove the control panel, do not disconnect the lines from the panel. There's a quick-disconnect plug, make sure it's fully seated. Mine came from the factory with one side not clipped.

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Unread 11-29-2012, 09:26 PM   #9
cgcarpenter
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Great that will help a ton...

And another question is I was reading about bad actuator above the gas pedal could also be leaking around there? Because I can't find any leaks under the hood..

And how tight should the hose on the reservoir under the battery be? Really tight right?
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Unread 11-29-2012, 09:35 PM   #10
KoreaZJ
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It's a vacuum line, snug is good. If the end is bad and stretched out, cut an inch or two off.
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Unread 12-03-2012, 11:11 PM   #11
cgcarpenter
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So I still can't find this leak... I took the hose off the reservoir cut off an inch and it fit snug and good but for good measure I left it off and tested to see if the reservoir was leaking but I had no vacuum in the lines...
What could this mean?
I took apart the bottom half of my dash and couldn't find a leak there either. But when I took the controls out the knob wasn't seated right on the inside so I fixed that thinking that was my problem and sadly no it wasn't.
So any suggestions would help at this point...
And another question is there any electrical things at all the could cause this or fuses or stuff like that I should check?
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Unread 12-03-2012, 11:57 PM   #12
KoreaZJ
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Check the other vacuum lines under the hood... from the vacuum reservoir to speed control servo, firewall tee fitting, and intake manifold connection (vacuum source).

Here's a description from another thread... HERE

Quote:
Originally Posted by ZeeJay1997 View Post
The broken line is the source of your climate control problem. The single line thru the firewall goes to the vacuum switch for Climate Cont.

It comes from manifold across the top of the firewall , tees out thru the wall (may be a check valve here), then tees to the cruise control, then to vacuum canister in bottom of battery box.

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Unread 12-04-2012, 12:00 AM   #13
cgcarpenter
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I've checked them with soap and bubbles... And nothing.

I had no vacuum at all when I checked the hose for the reservoir.. What could that mean?
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Unread 12-04-2012, 12:06 AM   #14
KoreaZJ
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Not sure a vacuum leak would blow bubbles since the air goes into the leaky line...

Look for a broken/missing/disconnected vacuum line. Only runs a few places... from the vacuum reservoir to speed control servo, firewall tee fitting, and intake manifold connection (vacuum source). Start at the intake end, there's vacuum there with the engine running.
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Unread 12-04-2012, 12:08 AM   #15
cgcarpenter
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Yeah when I popped the hose off I couldn't feel it? Should I be able too?

Over by the throttle body right?
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