Airflow issues...with a twist!

Airflow issues...with a twist!

Postby charlesives95 [OP] » September 23rd 2020, 2:30am

Hi all,

I am the proud new owner of a '98 Astro Van and have been lurking these forums for awhile and gotten a lot of helpful tips as I've gone about making small repairs to it.

Like many other vans of its age, mine had the issue where the airflow was stuck on defrost. Upon looking at the vacuum lines, it was clear that some of them were cracked and broken. I had my van at the mechanic for other reasons and had him replace those vacuum lines while the dash was taken apart. Now, the airflow controls work great, with one exception: the air isn't coming through the lower heater vents. It's diverting correctly, because I feel it coming out of the hole in the black box where the cabin air filter is in the passenger footwell, but for whatever reason, it is not coming out of either of the vents in the drivers' or passengers' footwells. Because the air is diverting correctly, this doesn't seem like a vacuum problem -- any ideas what it could be?

Also, this is the first car I've owned with a vacuum operated climate control system. Is it normal to hear a small vacuum-type sucking sound when the airflow direction switch is moved around?

Thanks in advance for your help and looking forward to contributing to this community!

Best,

Thomas
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Re: Airflow issues...with a twist!

Postby dchan51360 » September 23rd 2020, 8:50pm

Get a photo of the box by the feet of the passenger side.

There should be several plastic ducts coming off the box that route the air to various vents including one large flat-ish one that handles the vents behind the drivers seats if you have this feature. If they are there, you probably have blockages or they are just plain missing.

There smaller ones that branch off to go to each vent and when you take off the dash components very often they don't get put back correctly.
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Re: Airflow issues...with a twist!

Postby sixsix » September 23rd 2020, 8:51pm

Welcome!

charlesives95 wrote: ... Is it normal to hear a small vacuum-type sucking sound when the airflow direction switch is moved around?


Absolutely ... as you open, actuate, vent & close vacuum & elec. operated valves.
.

Well, after all... what would Banacek say ?... “Everything needs to change except the asshole culture and stupid way of life of the avg. antifa, BLM follower - slobs, cowards, killers w/o any thought that they, IN FACT, are now the Racists.”

.
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Re: Airflow issues...with a twist!

Postby charlesives95 [OP] » September 23rd 2020, 11:25pm

dchan51360 wrote:Get a photo of the box by the feet of the passenger side.

There should be several plastic ducts coming off the box that route the air to various vents including one large flat-ish one that handles the vents behind the drivers seats if you have this feature. If they are there, you probably have blockages or they are just plain missing.

There smaller ones that branch off to go to each vent and when you take off the dash components very often they don't get put back correctly.


Thanks so much, very helpful to know this – it's what I expected. Will get photos today or tomorrow and circle back. FWIW, I wasn't referring to the vents behind the front seats (my van does have them), but rather the vents in the front footwells that blow heat onto the front seat occupants' legs.
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Re: Airflow issues...with a twist!

Postby AstroWill » September 24th 2020, 2:05am

Welcome Thomas!
charlesives95 wrote:the air isn't coming through the lower heater vents. It's diverting correctly, because I feel it coming out of the hole in the black box where the cabin air filter is in the passenger footwell, but for whatever reason, it is not coming out of either of the vents in the drivers' or passengers' footwells.

We don't have any cabin filters that I have seen.
Should be getting airflow on bi-level, heater, and blend. All the ones with the down arrow on the control.

charlesives95 wrote:Because the air is diverting correctly, this doesn't seem like a vacuum problem -- any ideas what it could be?

Could be the controls, an actuator problem or a vacuum problem. I think it's the red vacuum line, follow/test that one.

charlesives95 wrote:Also, this is the first car I've owned with a vacuum operated climate control system. Is it normal to hear a small vacuum-type sucking sound when the airflow direction switch is moved around?

Yes but only when it's changing modes, then the sound should stop. If it doesn't stop, you have to check for leaks.
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Re: Airflow issues...with a twist!

Postby dchan51360 » September 24th 2020, 4:02am

The black box behind the passengers dash area has 4 exits as far as I know. there is a vent that comes right out on to the passengers legs. one hole is a larger one to the left.. This one ducts air to the floor duct under the seats, and to the drivers side foot area. One goes up (maybe 2) to supply the upper vents (the ones that blow in your face, in the middle of the dash) and the last one goes to the defogger.
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Re: Airflow issues...with a twist!

Postby charlesives95 [OP] » September 24th 2020, 9:00pm

All,

Air is coming out of the little holes in the black box you can see in this photo, instead of the vent above it. Hope that clarifies.
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Re: Airflow issues...with a twist!

Postby charlesives95 [OP] » September 25th 2020, 3:39am

Okay, pulled apart the doghouse and the trim in the passenger's footwell today to take a closer look and have better pictures to share. All the vacuum lines in the engine compartment have been replaced and the ones on the other side of the firewall going to the dash look good.

The problem:
The airflow selector, when set to "floor" mode, doesn't send air to the lower vents that are parallel to the drivers' and passengers' knees. Rather, as I said, the air comes out of the holes in the black box/duct type thing in the passenger footwell.

In addition, the bi-level mode doesn't really work – if you switch to bi-level from vent mode, it just stays on vent mode, and if you switch to bi-level from floor mode, it stays on floor mode.

My observations so far:
The two vacuum actuators on the right side of the passenger footwell seem to be fine – that is, the defrost mode actuator and the max a/c air re-circulator actuator. They are moving correctly as I turn the airflow selector dial around. That leaves the mode actuator, which is on the left side of the passenger footwell, or on the right side of the doghouse, as being potentially faulty. Alternatively, perhaps the doors themselves are stuck, somehow?

Issues:
-The mode actuator is no longer made. It's AC Delco 15-5550, or GM #15720385. If it did need to be replaced, is my best bet now a junkyard?
-If I need to disassemble the black box/duct type thing, how do I go about doing that? I see screws but when I removed them, the whole thing remained tight.
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IMG_2718.jpg
Here, you can see the ducting.
IMG_2719.jpg
Here are the two holes where air comes out of when the mode selector is set on "floor"
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Re: Airflow issues...with a twist!

Postby dchan51360 » September 25th 2020, 6:24am

Yup sounds like one of the doors internally is stuck part way. Can you move both of the vacuum actuators? One is for the floor vs face. and one is the defrost vs lower boxes.
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Re: Airflow issues...with a twist!

Postby charlesives95 [OP] » September 25th 2020, 6:50am

dchan51360 wrote:Yup sounds like one of the doors internally is stuck part way. Can you move both of the vacuum actuators? One is for the floor vs face. and one is the defrost vs lower boxes.


The defrost one is moving fine. I need to get back in there tomorrow and check the floor/face one, which is the discontinued part I mentioned in my previous comment that would be a real PITA to find and replace.
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Re: Airflow issues...with a twist!

Postby MechBob » September 25th 2020, 7:54am

So,the first "giveaway" not an astro van made that has a "fresh air filter:. Second,seems like you do not know about the other electric flap control devise,up in the heater unit,that controls air flow.hard to get to,hard to replace.But feel free to pick on me if I got it wrong,i am older.
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Re: Airflow issues...with a twist!

Postby sfeaversfeaver is online! » September 25th 2020, 4:36pm

Those vents only blow air when the dash vents are blowing, not on the floor setting. Bi-Level is a split between floor and dash vents. Try it on AC or Dash vent setting and you should feel some air. Its not a ton of air that comes out though in comparison to the dash vents. Maybe your searching for a problem that isn't there.

Hope this helps!

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Re: Airflow issues...with a twist!

Postby sfeaversfeaver is online! » September 25th 2020, 6:35pm

I just noticed, are you missing this piece on the passenger side? Goes behind that vent.

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Re: Airflow issues...with a twist!

Postby charlesives95 [OP] » September 26th 2020, 1:19am

sfeaver wrote:I just noticed, are you missing this piece on the passenger side? Goes behind that vent.

102846


Funny that you noticed this -- the piece was there, but it was disconnected. Now that you explained the airflow settings and which vents they correspond to, I think the system is working as intended. I reattached this piece and its coming out of these ducts on the "vent" setting -- weakly, but its there.

So, it seems like it was a non-issue :D thank you for your help everyone!
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