Added fresh/recirculate to Vintage Air system

[veloandy]

I found an uninstalled Vintage Air GenII Compac main unit for $150 on my local FB marketplace and installed it on my originally-aircooled/now-suby-powered Westy a couple of years ago.

A lot of other people have documented their Vintage Air installs and lamented the lack of a fresh air option, especially if the AC function isn't working and you need effective defrost. I experienced first hand how much of a bummer that is (thanks to a leaky refrigerant o-ring near the evaporator that required pulling the dash to fix)

Then, right after I started the van on a minus-20-degree-F night last winter I had the unit on defrost and the blower on high to prevent my breath from instantly freezing on the inside of the windshield, and the squirrel cage cracked. After it cracked when I'd set the fan to "high", the squirrel cage would get flung out and hit the housing and make a horribly disturbing racket (so I could only use it on low/medium).

Finally this summer I decided to fix the A/C, fix the blower motor, and add a damn fresh air option! Unfortunately, the VintageAir blower motor assembly was backordered for at least a couple of weeks (hecking supply chain disruptions!!). Tencent's air blockoff kit seems really good, but I wanted fresh air directed to my blower motor instead of just blown indiscriminately under the dashboard.

So, I bought:
* A/C O-ring replacements (to fix my refrigerant leak)
* DBW throttle body from a 2011-2019 Jeep Cherokee. The model of car it comes from wasn't important, but I chose this one b/c it's 3-inches in diameter and was only $10 + $7 shipping on Ebay.
* This 12V-5V converter from Amazon $12 (a USB adapter would work too)
* This universal blower motor from Amazon: $85
* This 3-inch flexible heater vent hose $10
* A big bottle of ABS cement from Home Depot
* A bunch of ABS sheet scraps from a local plastics supplier (Fort Collins Plastics -- those folks are super-cool)
* This pulse-width-modulated fan controller for $19
* A lighted button, and some other misc supplies

Basically, I pulled the dash and:
1. Unscrewed the fan blower assembly from the Vintage Air unit. The whole thing just unscrews and no cutting is necessary.
2. Removed half of the fresh air block off (which was easy to do b/c I blocked it off with aluminum sheet about the thickness of a soda can + aluminum HVAC tape, so I could just slice my blockoff in half with a razor knife

3. Used ABS and cement to build a half-blockoff plate with a standoff where I could mount the throttle body, and wired that up with the button through a 12V->5v converter Imgur video of it opening/closing

4. Used a lot of ABS scraps and cement to build a box with a toilet flapper valve that the blower motor mounts to that fits in under the passenger corner of the dash. Here it is before I cemented the top on to see the flapper valve:

The o-ring is some silicone tubing I had left over and a scrap of foam bedliner sealant tape to kind-of seal between the vent and the intake to the squirrel cage.
And here with dimensions and the blower motor attached. All vent hose connections are 3-inches diameter (cut from a T leftover from my Chinese Diesel Heater install):

And here tucked up in the corner of the dash before I built yet another ABS bracket to bolt it to the body:

(There's kind of a lot going on here b/c I also have a monoblock amp for my bazooka tube, aftermarket power lock wiring, and seat heater relays behind the glove box)
5. I used a chunk of the Vintage Air fan housing and a ton of ABS cement and aluminum HVAC tape to build a 3-inch round hose input to the A/C evaporator/heater core assembly.
6. I discarded the rest of the Vintage Air blower assembly, fan switch, and fan relay and wired it up. Here's before/after wiring diagrams:
Original Wiring:

Modified Wiring: Be sure to run power to the A/C mode switch & control module (it was formerly powered by the discarded fan switch)

And the pile of VA junk I discarded:

7. Then I ran the flex hose to everything under the dash, shoehorned the dash back on, evacuated and recharged the A/C system, and it works!!!

Performance
* It's hecking cold.
* It's nice to be able to draw in fresh air directly to the blower motor if I need it
* Fresh and recirculate are both equally quiet & I'm happy I don't think I added any additional wind whistles at speed
* I like that the fresh air vent throttle body closes when the car is powered off to keep mice, wasps, and other critters out when the van is parked.
* I like the continuously variable fan control from the PWM controller
* Driving at 80 MPH with the fresh air vent open results in a barely noticeable increase in airflow -- definitely not the same as the "extra open window" sensation you get with the full vent open with the stock air box. I'm not even sure there is enough fresh air forced through the system to close the flapper valve.
* I have the "face" a/c vents running to the 2 dash vents on either corner of the dash and one vent on the center panel below the dash/in front of the shifter. (so 3 total "face" vents)

On its highest setting with all 3 vents open, the airflow is marginally OK -- kind of like maybe 2-of-4 fan speed setting on a modern car.

If I close one of the vents the airflow is a lot better on the remaining open 2 vents: On its highest setting with only 2 of 3 vents open, the airflow is more like the 3-of-4 fan speed setting on a modern car

This is about how I remember the airflow of the stock Vintage Air system, but I don't have a good way to actually measure it, and I haven't had a "high" fan setting in a while so ¯\_(ツ)_/¯

* I think a more powerful blower motor would help a lot, but there's not a lot of room to mount anything much bigger (but if you're OK getting rid of the glovebox or aren't running a bazooka bass tube in the passenger-side footwell, you might have more options than me)
* I like that I still have the radio in the stock location and a stock and functional and unmodified glove box. I could have mounted the A/C controls in the dash instead of the cover below the dash to keep it even more stock-looking, but it sure was nice to be able to fully run and test the A/C with the dashboard off. I also like that I don't have to bend up the fragile-looking A/C thermostat capillary tube every time I R&R the dash.

If anyone comes up with improvements or ideas, post them up! Thanks!