TheSamba.com :: View topic - Front in dash AC evaporator as a rear system "Booster"

Sat Mar 26, 2016 5:42 pm

I'd love to see the schematic that accompanies that Nostalgic unit. I'm having a hard time understanding the plumbing required to run both evaps. What's the shut off valve for?

Sat Mar 26, 2016 5:55 pm

Just thinking.

Sat Mar 26, 2016 6:03 pm

Dave,

How many BTU's does that Sanden put out at any given RPM?
I'd look it up myself, but you came up with another model compressor in your van.

I'll give you what you should be looking for to power both evap's up efficiently.

27,000 BTU's at 2000 rpm's
42,000 BTU's at 4000 rpms.
Discharge rate 240 psi at 4000 rpms.

This is bigger than most home units, and more than adequate for 2 automotive evaporators.
This is the specs on a GM / Fridgidaire A6 compressor.
I think you're going to need at least this much to cool Momma down.

The Sanden is rated at 26000.
I think you might be trying to squeeze a little more outa it than It's capacity.

Sun Mar 27, 2016 5:22 am

Well....... Many people do a lot of things while being told that it cannot be done.
If I fail miserably? At least I thought outside of the box and gave it a shot. You all can have a good chuckle at my expense....... Dumb Stupid David......

Honestly, when it comes to Auto AC, if I had to choose I'd much prefer cold air blowing out of the dash onto my face and upper body over cold air delivered 15 feet away and boosted forward by a ceiling mounted fan, blowing on the back of my neck.

I purchased the electric shut off valve with the intent of using it to isolate the front unit from the rear, having the ability to turn off the refrigerant circulation to the front system completely if I found it neccessary due to design failure or as Terry points out, lack of capacity in the compressor.

I'm now thinking that I may be better served by using the solenoid to cut off the factory rear system completely and having the front system be always operational.

Having the front unit always at the ready will enhance windshield defrosting as well as provide instant heat relief with cold air delivered to the front occupants upon starting the Van.
Having the front unit gives me the ability to mix heat with the refrigerated air too, just like one of those modern cars!

Again, I have an 86 Vanagon with a Behr 2 Evaporator AC system here in my driveway. Inhave examined this system inch by inch, I KNOW how it works.

There are no huge compressors, there are no complex relays or refrigerant shut off valves.
There is a "T" in the 06 sized pressure line after the Rec/Drier sending high pressure refrigerant to the dash unit and also to the rear unit.
There is a 2nd "T" in the size 10 return line at the compressor sucking the return from both units into the compressor.

That's it!
It works great!
This Behr unit is a much sought after and coveted system by those who want two zone AC in a Vanagon.

Some photos of the Behr system.......

Closeup of pressure pipe leaving Rec/Drier showing "TEE" to feed rear Evaporator.

TEE on Pump Suction where return lines from both Evaporators join....

Dave

Sun Mar 27, 2016 7:04 am

Excuse the crude hand drawings but.......

Here is how the 1987 2.1 with the Behr Dual Evaporator system is piped.....

Red is Pressure
Blue is Return

The Behr system uses a Seltec DKS-15Ch. PN 506211-0992

The R12 charging ports are on the rear compressor cover.
As you can see, its about the same size displacement as my new Sanden Compressor.

FWIW..... I don't just wake up in the Morning and say "You know what? I'm going to install a second Evaporator today!" Believe it or not, There is a lot of research, thought, drawing upon decades of experience and planning that goes into most of my ideas....... My only "failure" in that I'd never recommend doing what I did is my gas tank metal fitting mod...... It works..... but really wasn't worth the effort. I should have welded.

Dave

Sun Mar 27, 2016 10:58 am

djkeev wrote: I'm so weak..... I just ordered the Nostalgic air unit! 8)

I also got a 12v AC control valve for the second evaporator that I'm adding.

http://nostalgicac.com/12v-freon-shut-off-valve.html

All is not lost though..... My Ghia convertible will love that vintage Evaporator!

Dave

my dad installed the vanagon ac himself. bought the van new, wanted ac option, dealer wanted too much for it installed, so he bought the van with no ac and got,the dealer to sell him the ac kit at cost.

my grand dad had a big Desoto car, he got ac too, the entire cold coil was in the trunk, no dash vents. all the cold air came out behind the rear passengers just behind their heads. the system was not designed too well, and the cold coils would ice up in high humidity. drive over a bumpy road or train tracks and ice would break off and be sent thru the blower, nothing like crushed ice on the back of the neck to,wake one up.

Sun Mar 27, 2016 11:28 am

Dave,

I cannot find any output specs on that Seltec compressor, except that it is a R-12 compressor, which means nothing.

I am reading anywhere from 10,000 BTU's to 40,000 BTU's, and from Greyhound Bus usage to John Deere's tractors..

You are not using that compressor in your Van, so, who know's if the Sanden you have bolted up will power up 2 evaporator's effectively?

You'll find out , I'm sure in no time at all--

It sure is a lot of work to be finding out what's going to happen.

Nothing Ventured, Nothing Gained--go for it.

Sun Mar 27, 2016 4:05 pm

You know, I was going to do some size calculations.......

But then my eyes glazed over and my mind went numb......

http://www.academia.edu/6435845/THE_LOAD_CALCULATION_OF_AUTOMOBILE_AIR_CONDITIONING_SYSTEM

I'm a "smart" guy but I'm not a SMART guy......

Dave

Mon Mar 28, 2016 9:22 am

Somewhere--somehow, you're going to have to come up with a viable formula for BTU output capacity required for what you intend to cool down.

There has to be something, somewhere where you can figure out the area, heat radiated off of the glass, roof, engine, radiator , etc.

This kinda info would certainly make your decision of what to do a bunch simplier.

Just tossing in an extra evaporator, with an undersized compressor --( all unknown at this point ) is a frutal attempt to squeeze more outa a pre-squeezed & empty orange.

You can only get so much out of the unit you have, and after that your just spinning your wheels here Dave.

Mon Mar 28, 2016 7:36 pm

I say go for it. Millions of Hot Rodders and garage wrenching guys would do the same.

Mon Mar 28, 2016 8:37 pm

Million of hot rodders are running two evaporator cabinets?
In a touring car, sedan or coupe?

You probably missed the first half of the show.
Went out for popcorn just after the credits.

Mon Mar 28, 2016 8:59 pm

Terry Kay wrote: Million of hot rodders are running two evaporator cabinets?
In a touring car, sedan or coupe?

You probably missed the first half of the show.
Went out for popcorn just after the credits.

Caught the entire show.

Think of it like adding a second carb to the model A , welding up the spider gears, cutting your first A pillar when doing your first chop, pulling a leaf from each front pack and adding taller tires in the rear or adding malt to your shake. Dave is doing something most wouldnt think of and has the honesty to post his altered path here. He doesnt need a heavy weight dragging him into the abyss of trial and error. So, in the spirit of guys like me that try stupid sheeeit without "running the numbers passed my local rocket scientist" and just attempt something outside the automotive box, go for it.

Pull the stir stick out of here and put it back in your Johnny Walker and Cherry Pepsi. Houston already has enough problems ;)

Tue Mar 29, 2016 12:53 am

Hey Dave:

Insomnia has me at my computer again - - trying to bore myself to sleep. Most of the OEM dual evaporator systems that I have seen (eg: Ford and GM SUV behemoths) use an orifice tube (AKA Cycling Clutch Orifice Tube or CCOT) as the expansion device on the main evaporator and a TXV expansion device on the secondary evaporator. The secondary evaporator then uses a solenoid at a tee to cut the flow on the liquid line after the tee to the TXV on the secondary evaporator. This gives priority to the "main" evaporator as the CCOT system allows a higher amount of refrigerant to pass through. The solenoid valve then is connected to the wiring that you used to use to power the compressor clutch relay on the factory Vanagon system.

Tue Mar 29, 2016 2:43 am

Thanks for the feedback and support!
BTW I know Terry is just watching out for me wasting time and money on something that he strongly feels will not work. No offense is taken. (Though on page 1 he told me to basically go for it)

Terry Kay wrote: So you are going to blow this setup into the heater intake?

Might be a bit off the wall but interesting idea.
The AC is going to blow outa the front vents--right?

As an FYIi..... I'm doing it! ....... so he can now wait patiently to scream "I told you it wouldn't work!!" :lol:
You all do know that I will honestly admit failure here if that is what it comes to.

I'm not going to completely redesign my system by removing expansion valves or mimicing GM. I do appreciate knowing how newer dual systems wotk though.

Back to the "model" classic Behr system...... It has Two Expansion valves, one at each evaporator.

I think that Behr depended upon the Expansion valve to act as a unit flow control valve. This allowed refrigerant in only as called for by either unit.

I figure my electric solenoid valve to be an "upgrade" to the Behr system.
With the solenoid valve I can absolutely remove one system from the AC loop.

The more that I ponder this, the more likely it becomes that it will be the factory rear system that I can shut down.
Doing so allows me not only "instant on" in dash AC blowing cold air on my overheated body but the refrigerated air is mixable with heat and can be directed out of any if the factory vents and also onto the windshield to defog.
We've all experienced "too cold" AC blowing out the vents of modern cars? We
add a little heat to cut the cold but keep the dehumidification properties of AC.

When my UD-110 arrives many questions will be answered, the main one being..... "Will it fit?"

Dave

Thu Mar 31, 2016 2:49 pm

Well, my Nostalgic Air Evaporator arrived a few minutes ago.

I AM SO EXCITED I ALMOST WET MYSELF!!!!

It is as if Nostalgic Air had a Vanagon in front of them and instructed their design team to design a self contained evaporator assembly that will fit between the wiper motor and the dash and from the Heater box to the steel structural bits!

It is a PERFECT fit!
Really...... It IS!!!! :lol:

I am going to plumb it into my modified heater box so I can blow it out any dash, floor or windshield vent and mix it with the heater air too.

But with a little creativity it would be easy to make it blow out above the glove box! Ducts could be run towards the drivers side if desired.

A few photos comparing it to my flea market Classic Air Cooled Beetle Evaporator that started this lame brain project! I picked it up at the All Air Cooled Meet last Fall......

Frontal view is almost the same size but it is slightly more narrow allowing a perfect fit up inside the dash......

These views clearly show how much smaller it is.......

I also ordered the electric solenoid pressure cut off valve. This valve will enable me to shut down the factory rear AC as/if needed to focus the compressors efforts onto the front system

Excited! Excited! EXCITED!!!!! :lol:

This Evaporator may very well be the Holy Grail of AC, the answer to easy and affordable in dash AC that so many seek.

Dave

Thu Mar 31, 2016 7:36 pm

Hey, wow! Looks like a great project!

Now for something definitely off-topic, sorry:

I'm not against doing it all with one compressor or anything, I'm just asking: is there room anywhere to put a second compressor? How about on a van with a conversion to Subaru, even with PS pump too... Just gets me thinking of keeping my complete rear system AND add a complete alternate dash with better HVAC up front. Just wonder if anyone has an additional device back in the engine compartment driven by belts? Is there room somewhere?

Thu Mar 31, 2016 8:08 pm

bobbyblack wrote: Hey, wow! Looks like a great project!

Now for something definitely off-topic, sorry:

I'm not against doing it all with one compressor or anything, I'm just asking: is there room anywhere to put a second compressor? How about on a van with a conversion to Subaru, even with PS pump too... Just gets me thinking of keeping my complete rear system AND add a complete alternate dash with better HVAC up front. Just wonder if anyone has an additional device back in the engine compartment driven by belts? Is there room somewhere?

then you would need a second condenser. maybe one can stack two in front of the rad otherwise put it under the body maybe.

I REALLY like the direction Dave is taking this project.

Thu Mar 31, 2016 8:29 pm

vanis13 wrote:
I REALLY like the direction Dave is taking this project.

X2 - Go Dave GO! Subscribed.

Thu Mar 31, 2016 9:18 pm

How are you planning on running hoses? Is your receiver/drier in your rear wheel well? If it is, thats a lot of extra hose to run from there to the front of the car and back to the compressor. Would be less hose if the rec/drier is located closer to the condenser

Very interested in what you're attempting. Im planning an overhaul of my ac system...I may copy your approach!

Fri Apr 01, 2016 4:04 am

I have a late production 1986 unit.

What this means is that it is a Bastard of design. There is no published literature that I've yet discovered that covers it.
The wiring is unique, the plumbing is unique and some features are unique.

It is basically the 1985 system, the rec/drier is in the LF wheel well so running an 06 size line to the second Evaporator isn't a major hurdle.

The 86 has the high speed fan, resistor and relay system though.
It does NOT have safety pressure switches or the 87 electrical panel in the LR pillar. (I added a binary switch at the Rec/drier during my rebuild)

It has the older compressor style exiting out the back without the side exit manifold.

I've ended up drawing my own wiring diagram for the system because I cannot find one put out by VW.

I do not see an advantage to, or a spot for, a second AC compressor. Terry often says an old GM fridgidaire unit would bolt up and provide plenty of circulation. There are newer more efficient units used today.... Would they fit? I don't know.

I'll continue to post as I Progress. Before running lines I'll pull the dash and plumb in the Evaporator to the heater to verify fit and operation before adding connections into the refrigerant system.

I Have several balls in the air right now, sliding door, trans reseal, axle repack.

The road salt is almost gone and hoping for a ride soon. :lol:

Dave