Increasing HVAC output volume

[SeanPwnery]

It's late May as I write this, and here in Texas, summer has already given us a pretty nasty preview of what's to come. Like many of you, I drive a Crew cab, that's at least 6 vents when the air is on, 4 big ones up front, widely spaced apart, and two token vents in the rear, again, with a long run to them. The actual temperature coming out of the vents after a few minutes is plenty cold - however despite having all 7 speeds on the blower motor, I feel like the volume of air coming out of these vents are similar to be breathed on by an asthmatic patient. Sure, there's air, but by the time the air leaves the vent and hits your face, it's barely there. On a really hot day, this could be rather annoying, and it feels like we're back in the 1980's leaning towards the vent trying to get that little bit more, that little bit quicker.

So, here's my point in all of this. Once upon a time, I used to build Jeeps - SJ's in particular, J-trucks, M-715's, Grand Wagoneers (real ones, not this bloated Grand Cherokee garbage we have these days), and Wide Track Cherokee S's. Those too had kinda weak air volume having 4 under-dash vents only. Back in those days, we were able to find upgraded "Squirrel cages" for the blower motors since AMC and Kaiser before them used a hodge-podge of everyone else's parts. Essentially, having a blower motor fan blade that matches the diameter of the OE one, but having much more pronounced vanes to really move a lot of air.

I'm curious if anyone out here found a similar "upgrade" for a 4th gen to do this. I'm almost tempted to buy an OE replacement, having it 3D scanned, and having one 3D printed with double the vane size to solve this, but if there's already a solution out there, I'd rather go that route. It'd be nice if the back seat passengers can actually feel a current, and me not having to choke off several vents to get the volume I desire. One last thing to note, yes, I replaced the Cabin Filter - but the volume change was the same.

 

[Mr. Wo]

Any chance the evaporator is clogged with debris. Dust can work its way into it.

 

[whiskytangofoxtrot]

I have a 2015 and I replaced the cabin air filter, if I remember correctly, you had to modify the airbox to make it replaceable. I live in Florida and we are pretty happy with the AC output but we don’t use it for many short trips

 

[Tremper126]

I was goi g to chime in it could be cabin air filter. Certain trucks came with them, others didn’t but you can buy a mopar kit with filter and door. Would be worth checking that. My 2014 Laramie didn’t have one, I didn’t add it either and it still throws a pile of air.

 

[SeanPwnery]

Quick little update : Mine does have the cabin air filter already there - replaced the filter twice now since I've owned it - I can definitely hear the blower doing blower things, but I'm starting to think a little higher up the circuit now.

I've seen several videos covering the recirculator flap/box upstream of the blower motor, and how in a 4th gen, it's more of a bellows-type device rather than an actual flap door like 3rd gens had (which were prone to breaking, landing over the blower wheel and choking 70% or more airflow until you pulled the door out or replaced it). I've seen a few videos now of people "reinforcing" the bellows which tends to crack and age over time which leads me to believe - surprise surprise ... another Mopar with plastics and trim issues... shocker (seems they just can't do plastic or rubber right in the 3 various models I own).

I have a new blower/wheel assembly just for the sake of having it - and may still explore ideas on making a larger vaned wheel - but while I'm in there, I'm definitely going to look at the air inlet box/bellows above it - I suspect I'm going to find my smoking gun there. I'm 99.9% certain I had better airflow when I was on the road last summer, and now it feels more like being breathed on by an asthmatic person ... or if you've ever owned a classic Ferrari or Lamborghini - that kind of "pathetic afterthought" of a blower system.

 

[BTdriver]

" ... or if you've ever owned a classic Ferrari or Lamborghini - that kind of "pathetic afterthought" of a blower system."

Classic Maserati is more like a mouse cough - "eh".

 

[SeanPwnery]

New update : I went ahead and replaced the blower motor this morning. This was probably the easiest one I've ever had to do - and I'll be making a video series on it when I film the second half.

Turns out the blower was okay, and I learned the resistor is built in - a nice, neat little package. 1 -trim tool to remove 3 christmas tree clips, the glove box door, the CAF, and three 8mm screws. I swapped it because it seemed like the original would "stop" faster than the new one with the old "spin it by hand" test. I thought maybe a bushing was beginning to wear so the new one went in. The blower volume change was insignificant.

As such, I believe my "airflow demands" are simply just more than what this will put out. I've since contacted my friend about 3D scanning the wheel, and printing me a new one with vanes 2.5x longer than the stock ones. We'll try this with carbon-fiber reinforced polymer with total infill. I want this to be stout if it works. If the prototype works, you'll all be seeing a video on the project, along with a link for anyone who'd like to purchase one. I'm going to make *zero* dollars on this endeavor - I'm only helping a friend add something new to his online store, and prototyping what may be a solution to a lot of you, and myself included. Stay tuned.

 

[SeanPwnery]

So... summer is here in full bloom, and once again, the a/c vents feel like I'm being blown on by an asthmatic. In this thread, I asked if any of you had thought yours was too, and I have few local people I can walk up and compare it to, but I came across a few videos of earlier 4th gens without cabin air filters, and how their evaporator cores clogged up with stuff from the outside. Mine had a filter, but to be perfectly honest, I can't say if the original owner did anything about them, or if the dealer I bought it from put the "2nd" one in after 106k miles before I put in one earlier this year. I changed blower motors, both the original and my aftermarket perform identically (mine has the built-in blower motor resistor since my a/c controls double up on the screen. The recirc system doesn't use a "door" like 3rd gens have that sometimes break off and get lodged over the blower intake - and my "bellows" appears to be intact, and swinging the full 90-degree sweep between outside and recirc.

I'm starting to wonder if maybe my core has 10 years worth of mung in there. The question I have is about a video I came across where a guy didn't pull the dash apart. Instead, he basically hole sawed the air box on both sides of the evaporator core, then used coil cleaner spray, a few brushes, and a little vacuum action to clean his out, then simply plastic-welded the holes shut with the parts he cut off. Worked perfect on camera as near as you can tell.

Before I go cutting anything, I had a different thought - what if the air flow went in the opposite direction with a major suction force... like say, you temporarily seal the ducting coming off the blower motor to a shop vac, and close ALL but one vent to give it an air "intake" and back-feed the system ... I wonder if it would be enough to "pull" the stuff back out the way it came...

Anybody ever try that?

This is the video in question I mentioned about cleaning the core.