Air coming out of vents not powerful

[Wajeep]

I get air out of all vents. When it’s on high, the blower motor is really loud but the amount of air coming out is not that powerful. All fan speeds work, but with how noisy the fan blower motor is when it’s on high, I feel that more air should be coming out of the vents. The airflow seems wimpy. Ideas?

 

[WestCoastDan]

Replace the fan and motor.
The squirrel cage may have broken vanes on it, thus reducing the amount of air that it can move.
I say to include the motor, but that's just one of those 'make it easy' things that I like to do.

 

[Modoc Guy]

Once you pull the fan and motor assembly out, take a mirror and flashlight and look in your air box for leaves and debris etc. I’d check the air intake under the cowl for debris as well. It could be plugged and slowing the air flow.

Check the FSM for how to remove the fan/ motor assembly, it’s easy.

If everything’s clear and clean, then maybe the fan motor’s the problem.

 

[morrsp]

Once you pull the fan and motor assembly out, take a mirror and flashlight and look in your air box for leaves and debris etc. I’d check the air intake under the cowl for debris as well. It could be plugged and slowing the air flow.

Check the FSM for how to remove the fan/ motor assembly, it’s easy.

If everything’s clear and clean, then maybe the fan motor’s the problem.

I have the same issue. I had the entire hvac box out from under the dash, cleaned it, replaced the switches, resistor, and fan / motor, but still have little air flow. The fan sounds like it really moving fast but with minimal output. Suggestions?

 

[TJ Jim]

Is it coming out on the floor at the same time? Maybe the door that directs flow is not sending the air in the correct direction?

 

[morrsp]

Is it coming out on the floor at the same time? Maybe the door that directs flow is not sending the air in the correct direction?

How do I fix it?

 

[JMT]

How do I fix it?

When you change the fan selector knob from off to circulating to feet only, to dash only, does the air change which vents it comes out? Or does it come out of every vent the same?

Could be as simple as a vacuum line in the engine bay or the blend door actuator.

 

[morrsp]

When you change the fan selector knob from off to circulating to feet only, to dash only, does the air change which vents it comes out? Or does it come out of every vent the same?

Could be as simple as a vacuum line in the engine bay or the blend door actuator.

Very little change between knob selections

 

[NCLife]

Very little change between knob selections

I am REALLY stepping out offering advice here, but I did just do a bunch of reading and work on this. There is a black box called a Vacuum Reservoir attached to your passenger side fender, underneath your battery. That box has a vacuum line coming off it that T's into the cabin and then runs over to the top of the engine. I believe if that box is missing, malfunctioning or the line is cracked or broken you will experience the symptoms you are. My line was brittle and cracked. I didn't notice from any symptoms like you, but when I was replacing my fenders. I had no idea what the black box was and hence began my journey of learning and me offering you some amateur information. Maybe some can fact check me.

 

[JMT]

Very little change between knob selections

You have a vacuum leak. Most likely in the engine bay. The small black tube mentioned by @NCLife is broken, cut, unplugged, or cracked somewhere. It’s up near the firewall and runs across the engine as he described. Easy to fix. Just find where it’s leaking. The auto parts stores sell rubber connectors for a couple dollars. Remove the offending section or plug back in.

 

[NCLife]

You have a vacuum leak. Most likely in the engine bay. The small black tube mentioned by @NCLife is broken, cut, unplugged, or cracked somewhere. It’s up near the firewall and runs across the engine as he described. Easy to fix. Just find where it’s leaking. The auto parts stores sell rubber connectors for a couple dollars. Remove the offending section or plug back in.

I ordered a used one from eBay for about $25. Interestingly it was too short and stretched too tight. It was portrayed as the right one for my Jeep and it I did get it on. My question @JMT based on your response. Can I cut that line inline and patch in an extension? Do they make inline connectors, like you might use to connect to pieces of PVC? The line is such a small diameter. Anyway, just curious thx

 

[Danarch]

Yes they do, here is a kit. I’m sure the auto parts store would have just a couple to sell. Get the connectors and hose size you need and just route it how you want it.

https://www.amazon.com/dp/B0B9RLC261/?tag=wranglerorg-20

 

[NCLife]

Yes they do, here is a kit. I’m sure the auto parts store would have just a couple to sell. Get the connectors and hose size you need and just route it how you want it.

https://www.amazon.com/dp/B0B9RLC261/?tag=wranglerorg-20

Thanks @Danarch

 

[morrsp]

Is it coming out on the floor at the same time? Maybe the door that directs flow is not sending the air in the correct direction?

OK, I have air coming out all vents slowly. When I push the bottom plunger in (one with Brown line connected) I get quit a bit more air flow out the bottom vent. Remove all the internal switch lines and checked them for leaks and I don't see any. Looking in the engine bay I found the black line which connects to the t and followed it to driver side where it connects to the carburetor manifold, but don't see any issues. What's next?

 

[macleanflood]

If you have a vacuum pump you can connect it directly to the line and verify full control operation before reassembly...and then fix your vacuum leak.

-Mac

 

[TJ Jim]

If you have a vacuum pump you can connect it directly to the line and verify full control operation before reassembly...and then fix your vacuum leak.

-Mac

OK, I have air coming out all vents slowly. When I push the bottom plunger in (one with Brown line connected) I get quit a bit more air flow out the bottom vent. Remove all the internal switch lines and checked them for leaks and I don't see any. Looking in the engine bay I found the black line which connects to the t and followed it to driver side where it connects to the carburetor manifold, but don't see any issues. What's next?

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@macleanflood has offered up a very good suggestion!

So position your eyes so you can watch the door move as you change positions on the control. Does it move enough to change air flow?
If not maybe your switch is not working. Have you inspected the position knob to make sure it doesn’t have a leak? You could probably hear it if it’s leaking.
I haven’t had my heater box open yet, but……one of these folks that has maybe can jump in here. Mine has blown out several pieces of foam, which I’m assuming is the seal on that door. If that is a seal foam and it’s gone you’d loose a lot of directional control.
You really need to get under there and observe if that door is moving as it should.

 

[macleanflood]

Smoke tester too...can borrow one from many auto parts stores. Plug it into the vacuum line and where the smoke comes out is your problem.

Also reasonably cheap on Amazon.

Vacuum pump...I personally would spend more for MityVac.

https://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-63391.html
-Mac

 

[ChasUGC]

I think one of the best questions here hasn't been completely answered. The question is: If you change the position of the air flow, does the air flow stop coming out of the other vents? For example, if you change the selector to the front vent, do you still feel air flow from the defroster or the bottom vent near your feet? If yes, that you still feel air flow from the other positions, then you likely have a vaccum leak issue or a bad door regulator. The loud sound could be an indication of a bad fan motor as others have stated, unless you just have a bad vaccum which would be answered by the first question, or maybe it is both problems, a bad vaccum and a bad fan motor.

 

[morrsp]

Well, it seems it was the short connecting type to the box under the battery. Swapped it with an L connector and there is an increase in airflow at all locations. Thanks everyone for your words of wisdom and guidance.

 

[ChasUGC]

Well, it seems it was the short connecting type to the box under the battery. Swapped it with an L connector and there is an increase in airflow at all locations. Thanks everyone for your words of wisdom and guidance.

Right, but you still haven't answered the question. Forgive my persistence. It is only meant to help. Is air coming out of all locations, when the selector is turned to one position? Air should only come out of the locations listed on the selector. I mention this because I had that problem with an old Mustang of mine and the problem was rotten vacuum lines and split vaccum lines at the actuators. I also notice that your brown vacuum line seems to be bent backwards on itself, and I'm wondering if it is being pinched.(Figure 1)