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Weak airflow: Clogged ducts somewhere?

8K views 25 replies 15 participants last post by  AstroWill 
#1 ·
To make a long story short, I purchased a 2001 Safari a few weeks ago. The A/C didn't work at all, so I replaced the blower motor, resistor, and connector and the A/C was back in business. At least that's what I thought. The A/C blows cold now, but the airflow out of the vents is extremely weak, even on the highest fan setting. The fan does indeed increase in speed as I turn the switch up, but it's still weak even with the fan speed cranked up all the way.

I removed the paneling covering the heater core, and noticed that the flap moves as it should as I cycled the switches between the top vents, floor vents, defrost, etc. Here's the strange part. When I turn the dial from "A/C" to "Max A/C," the fan speed increases and I feel the airflow increase a bunch when I stick my hand in the "gap" between the heater core and the flap. However, there is no change in airflow at all at the top vents. Airflow out of the driver and passenger side vents are both equally weak.

Is it safe to assume that the ducts are clogged somewhere, or is there possibly some other problem? Thank you.
 
#2 ·
Hey bud,
It's a common issue. Nothing(likely), is clogged. Get under the hood, look around the passenger side. Replace all the rotten rubber lines. Once you do that, you will be back in business. Thats it... $5 at your LAP, for some vacuum/windshield fluid hose(5/16 if my memory serves me correctly). There are tons of write ups on the subject, could be done with all the rubber lines in 10 minutes. There is a brittle hard plastic line, which would have to be completely replaced from Rockauto.com. Little more elbow grease, another beer, simple collection of tools(a screwdriver), and you'll have a new system.

Keep us posted and welcome aboard,
~Junior

P.S. I hope you brought some humor when you signed up to this forum. Many of us are knowledgeable clowns, like Lumpy :cheers: :lol:
 
#3 ·
Thanks for the tips, Junior. I've seen some YouTube vids on replacing the hoses, so I'll give that a shot.

I think I need to get educated on how the A/C system works. When I switch from '"A/C" to "Max A/C," what exactly is malfunctioning in my van right now? I presume that there's an actuator door somewhere that's supposed to be moving that isn't moving right now because of the rotted out hoses?
 
#5 ·
Max A/C is commanding the vent door to close off outside air and switch to recirculating inside air. It sounds like it's moving faster, but it's not. It's just become a closed system.
 
#6 ·
Kart Hauler said:
I think I need to get educated on how the A/C system works.
It's kind of simple, once you start getting dirty. The key to the A/C is simple, everything is about vacuum. From the engine. To the vacuum ball. Through the compressor. That's it.... Keep the compressor oiled and filled, replace the rubber lines, check the hard plastic line, and enjoy the fruits of your labor.
It's pretty uncommon for the vacuum ball to be faulty. A little tip I learned, if it has two vacuum lines(one in, one out). Trace the line, and look around the for more lines. I was missing two 4" lines that needed to be replaced, because they were stuffed in a weird location. Had I traced the lines, I would have found them. And solved my issue, 2 years sooner. Yea, I let that weak pressure A/C go on, and on. Never again!! I will be sure to replace all of them, anytime one goes out. Cheap fix, so not worth saving a few pennies on rubber line.

~Junior
 
#7 ·
I had a dorm room in college that was smaller than the inside of my van. It's a big, empty box. Hard to cool. There's likely nothing at all wrong with your system. Nature of the beast with our A/C systems.

I wish one of you inventive goofindas would figure out a mod for a super high power fan.

C'mon inventive goofindas... :whack:

Lump
 
#10 ·
When you switch to Max AC the door that closes is partially behind and next to the passenger side kick panel. Grab a flashlight and have someone else turn the control dial so you can see it move. If you try to do it yourself, you will most likely miss it by the time you get back down there to look. That panel blocks off the fresh air intake which is in the passenger side front fender. If you look in the opening between the door and the fender you can see the intake vent.

If your vacuum lines are okay or that doesn't fix the issue, the motor that controls that panel has 2 vacuum connections on it. One moves the door, the other goes back out through the firewall to the heater control valve and shuts off the heat. The vacuum motor is the last thing over to the right as you feel under the very front of dash, and the 2 vac connections are one over top of the other using rubber elbows. I have had them work loose in the past and need to be pushed back on to the port completely.
 
#11 ·
Lumpy said:
It's a big, empty box. Hard to cool. There's likely nothing at all wrong with your system. Nature of the beast with our A/C systems.
That thought did occur to me, but I've owned a ton of GM vehicles over the years, and every one of them had much stronger A/C systems. I know it also gets hot in Phoenix, but here in Texas we're blessed with heat and wicked humidity :) I'll look things over again today, and if everything checks out, I'll just have to accept the realities of sweating it out during the summer.

Don1806 said:
When you switch to Max AC the door that closes is partially behind and next to the passenger side kick panel. Grab a flashlight and have someone else turn the control dial so you can see it move. If you try to do it yourself, you will most likely miss it by the time you get back down there to look. That panel blocks off the fresh air intake which is in the passenger side front fender. If you look in the opening between the door and the fender you can see the intake vent.

If your vacuum lines are okay or that doesn't fix the issue, the motor that controls that panel has 2 vacuum connections on it. One moves the door, the other goes back out through the firewall to the heater control valve and shuts off the heat. The vacuum motor is the last thing over to the right as you feel under the very front of dash, and the 2 vac connections are one over top of the other using rubber elbows. I have had them work loose in the past and need to be pushed back on to the port completely.
Thanks for the suggestions, Don. I will definitely give that a try.

Dumb question: Should there be an increase in airflow out of the vents when switching for "A/C" to "Max A/C?" Right now, there's no increase in airflow, but a definite increase in noise. What's I find confusing is that when I switch to "Max A/C," there is substantial increase in airflow near the heater core when I stick my hand next to it. However, none of that extra airflow makes it through the vents.
 
#12 ·
Kart Hauler said:
Dumb question: Should there be an increase in airflow out of the vents when switching for "A/C" to "Max A/C?" Right now, there's no increase in airflow, but a definite increase in noise. What's I find confusing is that when I switch to "Max A/C," there is substantial increase in airflow near the heater core when I stick my hand next to it. However, none of that extra airflow makes it through the vents.
Yours does exactly what mine does. I don't think(?) there's supposed to be an increase. It should just switch to RECIRC when on MAX and OUTSIDE VENT when on NORM.

Like yours, mine has a lot of air flow right next to the heater box when in MAX.

Look up there, next to the passenger kick plate and see what happens when you switch to MAX, as Don suggests. We both found that MAX causes the door to open to the outer world. Just the opposite of what it should do. I'd be interested to find out if that's normal or does everyone's do that.

Lump
 
#13 ·
I really need to find that door and just permanently close it. I wish I had blocked it when I fixed the van and had the front end off.

I can do without the car next to me's exhaust smells and heat and air work so much better if it is drawing from inside the van. The cleaner burning than a gas engine diesels smell I good without. I know some don't but I actively avoid getting that air intake next to their exhaust. Because most smell real bad.

I think the door seals leak enough to provide enough O2 we don't asphyxiate.
 
#14 ·
Lumpy said:
Kart Hauler said:
Look up there, next to the passenger kick plate and see what happens when you switch to MAX, as Don suggests. We both found that MAX causes the door to open to the outer world. Just the opposite of what it should do. I'd be interested to find out if that's normal or does everyone's do that.
My van does the exact same thing. When switching to "Max," the flap moves to draw air in from the fender vent. When switching to regular "A/C" mode, the flap moves in the opposite direction.

I suppose the good news is that, just as you suggested, everything seems to be working just fine. That also means that I'll be sweating more than expected.
 
#15 ·
There is no increase in airflow. Airflow would be controlled by your fan speed. I think the increase in noise is because the inside air is being drawn through the another port across the AC coil and just is very loud. That is where the recirculation is actually taking place to supplement the rest of the air in the van. You don't get any increased airflow through the dash vents. This is also why your wife is always freezing in that seat. :mrgreen:

As far as that side vent door hanging open - that's what mine was doing. One of a couple things fixed it. Since I did all 3 at the same time, I have no idea which actually made the difference because i was just sort of testing things and it started working.

1. There was a really long screw holding the kick panel on. This may have been overtightened or too long and was blocking the travel path of the door. I'm sure that screw was replaced at some point since that panel had been off.

2. There are some rubber hoses behind the kick panel. I moved those around and pushed them back further toward the passenger door. I think these are the rear windshield washer hose, and possibly the drain line for the AC since that goes down behind the wheel. They could have been blocking the vent door or pinched in it.

3. There are 2 vacuum ports on the vacuum motor that controls that door to the fresh air vent. I pressed tightly on those 2 vacuum ports to make sure they were connected. One vacuum port runs the motor (may be an orange line) and the other port (light blue or light purple depending on how much light you have) which sends vacuum out to the heater control valve to shut off the heat. if you've deleted the heater control valve in favor of a ball valve, you might want to cap that port on the motor and the purple line and see if it makes a difference. Make sure the vacuum elbows on that motor are sealed tightly. You can hold your hand on the top of that motor and feel the shaft move when when you switch modes. If it isn't turning, then it could be the vacuum motor or the connection to it that's the issue. If it's turning but the door isn't moving, then I would say something is blocking the door, check for that rubber tubing being in the path of the door or the lower screw holding the kick panel blocking the track of the door. This motor is going to be on the right corner of the dash where it meets the kick panel ( on my 99 anyway). It feels like a round plastic ball on the bottom and the vac ports are one over top of the other on the side pointing toward the engine.

I have had this problem for years with the warm air sucking in - had several people look at it, and it only got fixed when I really started messing with it myself. Wish I had torn into it years ago.

Hope this helps.

edited for typo
 
#17 ·
My 01 Astro does exactly the same thing as the OP. I've had the dash apart a few times over the years and checked the vents and flaps, but everything seems okay. I have cold air and all hvac controls work properly, just not strong enough air flow. I bought the van new and I can't remember it being like that back then. Must have been a slow process. I'll be watching this thread looking for a real fix.
 
#19 ·
Roger Ramjet said:
My moms car also a GM vent system had some sort of mouse insulation crap in it ,,

Has anyone ever figured out why a 97 Astro blower motor won;t go on high .. ?
One of a couple possibilities:

1. The blower motor is going bad - you can test it by using a jumper wire and hooking 12 volts directly to it and see if it goes at high speed.

2. More likely - the blower motor resistor is bad and has burned or melted part of the plug. It's an easy fix if this is the problem. Use the search function on the site for the term "blower motor resistor" or the term "blower module" and there are many threads on it,

If you need more info than is contained in the search results - best to start a new thread as your question is buried in a totally different topic posted by someone else.
 
#20 ·
Don1806 said:
Roger Ramjet said:
My moms car also a GM vent system had some sort of mouse insulation crap in it ,,

Has anyone ever figured out why a 97 Astro blower motor won;t go on high .. ?
One of a couple possibilities:

1. The blower motor is going bad - you can test it by using a jumper wire and hooking 12 volts directly to it and see if it goes at high speed.

2. More likely - the blower motor resistor is bad and has burned or melted part of the plug. It's an easy fix if this is the problem. Use the search function on the site for the term "blower motor resistor" or the term "blower module" and there are many threads on it,

If you need more info than is contained in the search results - best to start a new thread as your question is buried in a totally different topic posted by someone else.
Sorry I did not mean to try and interupt the OP posting . But thanks for the information .
 
#21 ·
Not a problem. A new question usually gets buried deep when it's in a different thread, and in many cases no one sees it because they have already read that topic and don't come back to it. Just didn't want you to wait for days on end for an answer if you needed more info.
 
#24 ·
Mine was the same way, I changed out fan motor, replaced all vacuum hoses and still the same. I decided to remove the mess that is the heater control valves, and by pass the rear heater to minimize a bunch of hoses. And low and behold, my AC problem was cured. I guess one of the diaphragms was bad. But I am happy now.
 
#25 ·
Oddly, I don't think anyone has mentioned if a dirty or clogged evaporator unit or heater core could restrict airflow?

Airflow on my 92 is fantastic!
Airflow on my 2000 main vents is weak (vacuum, relay, and fan motor are good).
Thankfully I have dual A/C units.
 
#26 ·
Mmusicman said:
Oddly, I don't think anyone has mentioned if a dirty or clogged evaporator unit or heater core could restrict airflow?

Airflow on my 92 is fantastic!
Airflow on my 2000 main vents is weak (vacuum, relay, and fan motor are good).
Thankfully I have dual A/C units.
Yep, seen crap blocking the evap, easy to check. It's usually a low vacuum issue but if you have already ruled that out...
 
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