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No Air through Vents

 
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Old 02-05-2019, 06:12 PM
Vsmith
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No Air through Vents

Hello! I have been battling my air system in my 98 Ford Club Wagon(E350) 15 passenger V8 5.4 for two years now. My first issue was solved by replacing the blend door actuator. Then one of my AC vacuum lines broke so I rerouted it with a new line to get AC again! Now at the coldest time of the year, I am not getting any air through the vents. The rear vents blow air but only cold air. I am not too concerned about fixing the rear system at the moment.

I can hear the blower fan blowing. The heater core gets hot and I my fluids are at the correct level. I can feel cold air blowing right above the heater core area. I have tried to manually close/open the blend door to see if that produces air but that has not worked. My blend door doesn't close all the way unless I take the actuator off and close it manually. It leaves a 2 inch gap between the door and top the area. Is that normal? I am missing a little bit of foam that I need to fix and that could be cause of my gap.

I have tried to manually open and close the valves?(silver round things with black bases, metal arms that are connected to various colored pressure lines on the top of dash area) That does not give me any difference in air coming out of the vents.

When I turn my control **** to different setting it sounds normal.

My guess is there is vacuum line broken somewhere that I am missing. Is there a specific line to check that make air blow out of the vents?
 
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Old 02-07-2019, 07:00 AM
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You'll need to check for vacuum leading to the Function Control located on the dash board, its the Heat, A/C, Vent, Defrost etc etc. Here's a photo of where the vacuum harness for the air flow control is located:



This is the back side of the Function Control Module:



And this is the schematic for the air flow control system:



HTH
 
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Old 02-07-2019, 07:19 AM
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If the blower is running and pushing air, the air has to come out somewhere (although not where you wanted it.) The usual failure mode, when vacuum is lost, is for it to exit out the defroster vents.

So, where is it actually coming out?
 
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Old 02-07-2019, 01:11 PM
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Originally Posted by projectSHO89 View Post
If the blower is running and pushing air, the air has to come out somewhere (although not where you wanted it.) The usual failure mode, when vacuum is lost, is for it to exit out the defroster vents.

So, where is it actually coming out?
After putting the cover back onto the heater core are it seems the air comes out of the defroster vents. I can see the vacuum with the yellow and orange line moving as I change the functions. The vacuum with the blue and white line moves as well when it is in the vent position. The only time I get are out of the vents in the vent position now. I think I was not getting any air before because I had the heater core cover off to see if it was getting hot. I unplugged everything from the back of the function control and plugged them back in.

Even though the arms moving on the vacuum could the flaps be broken that they are attached to? I am also thinking that the heater core may not be getting hot enough. If nothing else sounds wrong with the system to you guys I am going to try and flush the heater core.
 
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Old 02-07-2019, 01:13 PM
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Thank you for the pictures! This makes describing everything much easier.
 
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Old 02-07-2019, 02:15 PM
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The temperature of the heater core has nothing to do with the selection of where the air comes out of the system. A restricted core would result in a symptom of "no or inadequate heat" while still having control of the blend door.
 
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Old 02-08-2019, 11:46 AM
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Originally Posted by Vsmith View Post
Even though the arms moving on the vacuum could the flaps be broken that they are attached to? I am also thinking that the heater core may not be getting hot enough. If nothing else sounds wrong with the system to you guys I am going to try and flush the heater core.
The heater core condition has no bearing on air flow being properly directed according to the Function Control--even if its not in place the air flow should still be directed accordingly. As you observe even if the visible vacuum motor moves in sympathy with its selected signal through the FC you could very well have a broken panel/floor door.

Try moving the right side vacuum motor under the center of the dash by hand to see if the attached arm moves and/or air is re-directed.
 

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