No air on driver vent only

[jollyjerry]

Has anyone run into this before? Here's what I've noticed and looked at so far:

• Air blows when set to defrost or foot. I can also see the mode door actuator turn when I twist to different vent settings (defrost, foot, front)
• It sounds like it's blowing harder when changing fan from low to high. This makes me think the blower motor resistor works
• No air comes out of the driver side front vent at any fan speed or any vent settings

I haven't tried AC yet, and I started pulling off the dash panel, but it's getting dark. Does anyone have ideas for diagnosing this problem?

 

[east302]

Sorry, duplicate post

 

[east302]

No air comes out of the driver side front vent at any fan speed or any vent settings

Does air come out of the other three dash vents?

If so, then I'd say it's obstructed somehow. It's not a complicated setup--the mode door actuator adjusts to send air either to the floor, vent or defrost and that's about it. Pop the dash vent out and see if you see anything. There's also a flexible hose that connects near that vent which feeds the knee vent under the steering wheel. You might take a look under the dash and see if anything looks odd with that.

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[jollyjerry]

Thanks east302 for the diagram. Probably a dumb question, but what manual did you get that from? I'm trying to find a set of factory service manuals, but they're pretty pricy.

I did see the flexible hose going from the driver front vent to the knee vent, but neither of those are getting any air. I went ahead and cleaned out the dirt in the blower motor compartment mentioned by this thread and this video. I think I feel a little air coming out of the driver vent now, but it's so weak I might be imagining it. This makes me think the blockage is in the air ducts themselves.

What does the recirculate button do? I notice less air comes out when recirc is on.

 

[east302]

The duct sits/connects to the air distribution case indicated by the arrow. Once air passes through this, as directed by the damper controlled by the mode actuator, there is nothing else in the duct between that point and the dash outlets.

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Just to make sure...you said that you can feel air out of the other three dash vents but not the far left vent. Correct?

If you were not getting any air out any of the four dash vents, then I'd say either the mode actuator is out of sync/isn't working or the air door itself has dislocated.

The diagram is from alldatadiy.com. Subscriptions are pretty cheap.

When you press the recirc button, it closes the fresh air intake damper and air is drawn from inside the vehicle. With the blower removed, you can see the damper behind it.

 

[jollyjerry]

I checked just now. With the mode set to front, I get air out of the front center vents by the cup holder, and the two side defrost vents, but not the top defrost vent. That seems all out of whack. I'll pull off the mode actuator tonight and try twisting the spline manually.

Good to know there's just one vent going to the three. I might also try threading in a string from the front center vent down to see if there's any blockage there. Though that seems unlikely. I hope I don't have to pull everything out like your photo :/

 

[east302]

Manually twisting the actuator might mess it up, but I hear that they're available at parts stores and not that expensive. Here's the removal/installation procedure for a 1998, it looks to include the syncing procedure to make sure that it lines up. You could try removing it, resetting it and putting it back on.

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Here are pictures of mine (1998) showing the location of the index mark in full defrost, full floor and full dash/panel settings. You might see if yours match.

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You didn't say...do you get air out of the far right (passenger) vent along with the center vents?

I think I read somewhere that the bottom part of the case can be removed along with the floor vent. That might give you a better look at the mode door in case something is jacked up in there.

 

[jollyjerry]

My mode actuator indexes matches up with the photos you posted.

I think I read somewhere that the bottom part of the case can be removed along with the floor vent.

Yup, I tore this off initially. There's a single 7/32" screw holding it in. I can't really see into it, but I can reach in and feel the door change when the vent modes are changed. When the mode is set to front vents, the door is fully closed. However, with the fan set to high, a little bit of air is still pushed past the doors.

You didn't say...do you get air out of the far right (passenger) vent along with the center vents?

In the diagram you posted above, I don't get air out of 3, 5, and 6 in any setting. The weird part is I do get air out of 4 when set to front vent and defrost. When set to front vent, I also get air in the side defrost vents 2 and 9.

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I'm guessing the defrost and front vents don't share an input. Does the attached image look right?

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[east302]

I'd remove the dash vents (especially the center one) and use one of those small extendable mirrors to see if you see anything in the duct. Use a mirror on the bottom of the air distribution case as well, maybe you can see if the seal or something has come apart up in there.

I also get air out of 2 and 9 on both front and defrost settings.

On the air box, I would guess that the section closest to the windshield is the inlet for the defrost.

 

[jollyjerry]

I took off the dash bezel and threaded an extension cord through the vents to check that the ducts are not obstructed.

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I wish I tried running the fan before running the cord through it because afterwards, there air does come out of all the vents. Nothing fell out or felt like it got pushed out of the way. The air still feels weaker than the bottom vent, but I think that's just from traveling a longer distance and being split across more vents. Fan speeds 1 and 2 work as expected, but when switching from 2 to 3, there's an audible click, and it feels like the front vents lose pressure. Feeling the mode door while changing this showed that the air gets stronger, but blows past the vent door. When I went to turn off the air, the counter weight for the mode door fell out.

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If I reach in and gently push the mode door, I can feel a little play in the door and see the mode actuator spline and the counterweight mounting move a little. My guess for why the air pressure drops at higher fan speeds is because the mode door isn't sealing as well without the counterweight. Though even if I hold the door with my finger, I can still feel a lot of air rush by, so perhaps the door seals have worn too thin. Seeing how weak the air is, I'm thinking of sealing off the bottom with a plastic wrap before I reinstall the cover. This means there'd be no air going to the vents behind the front seats mounted on the floor, but I feel that's worth the extra pressure going to the front vents.

Thanks again for all your help! This'll make our July 4th camping trip in 90F weather **much** more enjoyable.