Front Vents not working

JBFury

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82 Gran Fury: I can turn the air on and it will only blow from the floor and dash, not the front vents, regardless of each button being pushed. I've followed the vacuum line from engine to console and it's in good shape along with the seven multicolored hoses and their connection points. Couple of questions.
1: Do the front vents only work when the a/c is charged and running (clutch not kicking on due to no refrigerant at this time).
2: Is there an ac clutch fuse and if so, where is it located.
3: How do I pop the passenger side lower panel off to access the blower motor? It seems to be riveted on the bottom with no screws, unlike the driver side.

Thanks for any suggestions and info. Small annoyance that I'll be happy to get resolved.
 

Mikes5thAve

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I think the vents are only for a.c, that's how it seems to work in a lot of cars.
That panel doesn't come off without removing the whole dash, you have to squeeze the motor out from the bottom.
 

Aspen500

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There should be air from the dash vents in A/C and VENT. Doesn't matter if the A/C actually works or not. A/C is just VENT with the compressor running.

Provided the vacuum switch (buttons) isn't broke, the other thing could be a disconnected vacuum tube or the heat/AC actuator diaphragm is leaking and can't open the vent door. It's the larger of the 2 vacuum motors on the left side of the HVAC plenum. Should have a red and a brown vacuum tube.

The one with the single yellow line is the heat/defrost actuator and is the smaller one. The actuator on the far right above the blower motor is the recirc actuator which closes the outside air in MAX A/C. In MAX, the water valve under the hood also closed to prevent coolant from flowing through the heater core.

I have seen the terminals overheat and melt at the mode button assy from poor connections and can cause the blower motor to not run. You have to pull the control out and look, if there is a problem with the blower motor not running. There is also 2 single spade connectors and those are for the A/C clutch.

Thee is a fuse, IIRC it's 20 amp and is also for the turn signal flasher and back up lights. (I'm going by a 1979 Factory Service Manual but in most cases it's the same for other years also)
 

Mikes5thAve

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You're right. I meant the a.c. Button in general, whether it's pushed in or pulled out to disengage a.c. Itself. The system reacts to the button being pressed, not if there's a charge in the system or not. Does anything change at all when the buttons are pressed? It might not be getting vacuum to the controls at all. Usually the biggest problem is the hoses breaking apart in that connector piece but you already checked that.
 

JBFury

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Regardless of what button I press nothing changes. Air will always come out of the defrost and floor panel but wont change over to vents. Speed control works. Ive checked the hoses three times thus far and I mean they look dang near brand new to my eyes. No fading, cracks, stress marks, all are plugged in and solid at all connected points. It's really making me scratch my head here.
 

Mr C

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According to the FSM, a problem with air distribution is one of 4 things:

1)Faulty vacuum actuator (it's on the end of the air box)
2)Vacuum line pinched/ disconnected from actuator
3)Air duct restriction (something in there...mouse nest etc.)
4)Faulty selector switch
 

BudW

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There is a black (hard) plastic vacuum line going from the intake manifold to the firewall. Actually, there are two hard plastic vacuum lines, one black (vacuum source) and gray – which goes to the hot water valve. That hard plastic lines have a tendency to break causing a vacuum leak (to engine) and no vacuum getting to the A/C control head – which is what I think has happened.
20161201_125857r m.jpg

From my '86 Fifth Ave - the yellow arrow is vacuum source from intake manifold.
20161106_161411 m.jpg

A fellow forum board member's /6. The green circle is the hot water valve. The gray line from it (marked by red arrows) meet up with the black line and goes through the firewall at the orange circle.
If either of these tubes are broken, then take one part to a parts store and get about 1 foot (1/4 meter) of vacuum hose. Then cut off about 1 inch (2.5 cm) of that to splice that break.


Annotation 2019-12-17 172134.jpg

The gray arrow shows where the two lines go though firewall inside.

Under the dash, there is a vacuum line coupler that has a tendency to crumble over time (purple arrow, above and picture below).
20191214_144136.jpg

The half of that connector that crumbles will be impossible to find - but can be fixed using the vacuum hose. Cut off a hose from the "un-crumbled" connector and scrape away the remaining crumbles on the other end, and use a 1 inch section (per break) to fix by matching up the hose colors. If something is not matching up (not sure), write back for I might have something for you.

BudW
 

JBFury

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So far I've pulled the dash and checked the vents for obstructions (none), followed all hoses and they all appear to be in good shape, couplers are surprisingly great condition, took out blower motor and it's running. Still no vent action though. I've pictured the dash control top and back if your eye notices anything.

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BudW

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Start the car and see if you have vacuum at any one of the ports on your last photo (above).

Did you follow the black tube from engine to where it goes into the firewall?
 

JBFury

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I did and I found a break. Patched it with washer tubing and we have air!!!! Thanks for all the help. I've looked over that line 20 times and somehow didn't see/feel the hole.
 

JBFury

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Actually at 2 points on the vacuum from the engine mount. Both relatively close to the connecting point, on the underside, close enough you couldn't turn the hose, just happened to feel it on the last look over. It was a clean slice missing at that, no idea what caused it.
 

JBFury

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Actually it looks melted. Again, no idea how I missed this.

20210730_212856.jpg
 

Mikes5thAve

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At least you know what to check next time.
Most cars when there's a problem like no vacuum it defaults to defrost.
 
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