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HVAC Control: Everything defaults to defrost

P

PurpleMystique

Hard-core CEG'er
Joined
Nov 16, 2004
Messages
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Location
Greater Des Moines Area
With warmer weather on the way, I figure I better get this figured out before I get stuck without A/C.

Since my 3.0 was put it, all of the HVAC positions besides "Off" turn on the defrost, and even when it's "Off," there's still a little bit of air coming out of the defrost, the temperature setting makes a difference.

In simple terms, what can I look at to troubleshoot this problem and determine the cause here?
 
Verify you did not disturb the vacuum line that runs through the dash that supplies the HVAC control head.

Inspect the vacuum motor directly above the accellerator pedal to verify the motor shaft has not come loose from the bell crank arm. This one is a common failure.

Steve
 
projectSHO89 said:
Verify you did not disturb the vacuum line that runs through the dash that supplies the HVAC control head.

Inspect the vacuum motor directly above the accellerator pedal to verify the motor shaft has not come loose from the bell crank arm. This one is a common failure.

Steve
Click to expand...

PurpleMystique said:
Everything looks good down there.
Click to expand...



What about here?
projectSHO89 said:
Verify you did not disturb the vacuum line that runs through the dash that supplies the HVAC control head.
....
Steve
Click to expand...

Open the hood and check the vacuum lines that run from the UIM to the firewall. One is probably cracked or broken.
 
how about this one .... if the system is off and is turned on it will default to the defroster. but if you turn it to the defroster and then click back to say the panel/floor setting it will work correctly.

I figure there is a vacuum leak somewhere, maybe at the controls since I removed those awhile ago .... and now I loose brake pedal vacuum assist before starting the car in the morning ....
 
there is also the possibility that the control rod going to the defrost door actuator came off and needs reinstalled. it was a common problen on the older tours but can hhappen to any year. you can access it on the drivers side of the vehicle above the center console. unless you have a problem inside the hvac box itself, it is either the problem i mentioned above or the lack of vac. as stated in the other posts.
 
BrApple said:
how about this one .... if the system is off and is turned on it will default to the defroster. but if you turn it to the defroster and then click back to say the panel/floor setting it will work correctly.

I figure there is a vacuum leak somewhere, maybe at the controls since I removed those awhile ago .... and now I loose brake pedal vacuum assist before starting the car in the morning ....
Click to expand...

No matter what I do, it will only go to defrost. I'm going to check the gray vacuum line through the firewall after I eat supper.
 
n16908665_36383267_335.jpg


Look good?
 
check the vacuum lines going in to the HVAC (behind the center console, access from either side, but I prefer passenger's)
 
Here, in all of its MSPaint glory, is a diagram of my vacuum lines.

vacuumlinesnf4.jpg


The brownish "X" is where the mechanic melted a small plastic tube closed. The question mark is a hard plastic line that goes down far enough that I can't follow it.


How does this look?
 
I have the exact same problem and I checked my grey vacuum line and its connected to the manfild but its not connected to where it should go through the firewall. Now I need to know where it plugs into by the firewall? Its really tight back there to see anything from the top, do I need to raise the car to access it fom the bottom? Where is it located?
 
From what I've been told, it's easier to see from underneath. Apparently, it's on the driver's side of the coil pack, underneath the two metal heater lines coming through the firewall. I haven't found it yet, but my car's currently up on ramps and the engine is cooling off so I can go dig in in a little bit.
 
Okay, it's fixed. The gray vacuum line had apparently rubbed against the header and melted. I replaced it with some new vacuum line and suddenly everything works perfect.

I pulled the coil pack and plastic wire harness to replace an O2 sensor and was able to get to everything back there.

Here are the old lines:
n16908665_36419742_3764.jpg
 
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