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djsixbillion
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PostPosted: Sat Jul 16, 2016 8:41 pm    Post subject: Dual A/C System Planning Reply with quote

So I've got the Small Car dash AC system on order, and would like to install it as a supplement to the stock rear AC in my 1990 Syncro Westy. Some pertinent details:

*The van has a 1.8T swap, and I'll be using a Sanden compressor, either the SD7V16 that came with the motor, or a Sanden 4653 as recommended by another user here as a fixed-displacement model with the same mounting configuration.

*The stock AC system is functional, but loses charge quickly. I cleaned the system all out and recharged it about 2 years ago and it cooled decently for a few months, but I'm guessing the old hoses have just given up the ghost.

*Will be using the Eaton EZ-Clip hose system, with GH001 hose and Red Tek as the refrigerant.

*Condenser will be replaced with a Nostalgic Air parallel-flow unit.

My goal is to maximize simplicity and use as much factory wiring as possible, and to that end I think I've come up with a way to tie the two units together as shown in the attached diagrams that will only require one wiring splice from the thermostat switch of the Small Car unit into the stock Vanagon AC relay. The systems should be able to operate independently.

Questions still floating in my head:

1. Will this wiring scheme work? I would be leaving the stock trinary switch in place to monitor pressure in the system, and with the two evaporators plumbed in parallel I don't see why any other pressure switches would be necessary.

2. Will I need a second receiver/dryer in line before the front evaporator, or will the factory one in the stock location suffice for both evaporators?

3. Is #10 hose sufficient for the return lines from the evaporators to the compressor? I noted that the stock system uses #12 sized hose, but with #10 fittings, so I'm not sure the extra flow capability of the larger size hose is really needed.

4. Any other thoughts appreciated!

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djkeev
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PostPosted: Sun Jul 17, 2016 4:45 am    Post subject: Re: Dual A/C System Planning Reply with quote

You aren't inventing the wheel here, Behr provided a dual evaporator system for these Vans for many years.

It isn't complex with zone valves etc.
Just one compressor (not even that big of one) one Condensor, one Rec/drier.
They Utilize simple in line T's.

I would bite the proverbial bullet and upgrade your existing system now.
New hoses, new condensor, new rec/drier, yes, even a new A/C compressor.
Why invest so much time and money to build a dual zone system but use the worn out leaking parts that are now installed?
Do it once, cry once over the price and be done with it!

This thread talks about an in dash unit and I posted drawings of the Behr system as well as photos.

http://www.thesamba.com/vw/forum/viewtopic.php?t=570707&postdays=0&postorder=asc&start=0

I am also building my own dual evaporator system using Behr's concepts.

http://www.thesamba.com/vw/forum/viewtopic.php?t=638024&highlight=

Hose upgrades as well as an entire system rebuild is covered here.......

http://www.thesamba.com/vw/forum/viewtopic.php?t=583818

The advantages of using RedTek....

http://www.thesamba.com/vw/forum/viewtopic.php?t=292488

And finally, it is too bad you purchased the smallcar kit already, for iulian in this thread finally came up with a Evaporator retrofit into the standard front air box!
This is so much cleaner and maintains original function. It isn't "plug ans play" but is fairly straight forward.
Add iulians system with Vanistan's ram air vent and you are golden!

http://www.thesamba.com/vw/forum/viewtopic.php?t=651327&highlight=fresh+air

The Smallcar kit is invasive and makes compromises that you may not wish to make.

http://www.thesamba.com/vw/forum/viewtopic.php?t=535444

Hope these links help, it's a LOT of reading but very informative.

Dave
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djsixbillion
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PostPosted: Sun Jul 17, 2016 1:24 pm    Post subject: Re: Dual A/C System Planning Reply with quote

Thanks for the reply Dave. Believe me, I've read just about every AC-related thread out there! I also saw the Diava unit that some folks have used. Thought about that, and it looks like a great option but lots of fiddly plastic trimming and gluing required - i.e. I would likely botch something and end up unhappy with the end product.

I'm not planning to reuse any of the existing AC components, except for the evaporator and wiring. Was originally going to just redo the factory system with new hoses, etc., but like you said, I want to do this only once and really don't think the factory system is adequate for full family comfort in 100-degree plus temps. By the same token, I don't think a front-only AC system would be adequate either - be it the Small Car or the Diavia - hence the desire for a dual system.

Also not really concerned about losing the fresh-air capability from the dash vents. When the outside temps are sane enough to make fresh air an option, I'm happy to crack a window or use the wing windows.

So all that being said - do you think the system will work as I have it laid out? I actually based the layout on your diagram of the Behr system - two evaporators in parallel with simple T-connections. Hoping it can be that simple...

Thanks again!
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PostPosted: Sun Jul 17, 2016 1:40 pm    Post subject: Re: Dual A/C System Planning Reply with quote

No, the reciever drier needs to be up front by the condensor. After the gases pass through it you have your T to each evaporator.


Size 8 hose Compressor to Condensor
Size 6 hose condensor to receiver drier to Evaporators
Size 10 hose Evaporators to compressor

Remember size 8 enters the top of the condensor, size 6 exits the bottom of the condensor.


I haven't looked at the wiring but I will.

Also from my travel experiences across this Nation in August..... You WILL miss the in dash fresh air.
I cannot imagine dealing with open vent windows and their related noise.

That being said, many are indeed happy with The same unit you pkan to use.

I had an extra Heat box assembly but I gave it away to another member here in NJ doing an air to water conversion.

I'll pay freight but I'd love to have a box to play with and see how the underdash unit I have fits into the air box.
I'd gladly pay shipping if you would be so kind....... 🙏

Dave
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ThankYouJerry
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PostPosted: Sun Jul 17, 2016 10:31 pm    Post subject: Re: Dual A/C System Planning Reply with quote

Have you discussed your plan with Small Car? I did. They told me "Front, rear, but not both with my 1.8T." I'd like to hear differently. They also told me the best they've seen at the vent with their front AC system is 55F. Not impressed at all. I currently have 42F at the vent with the OEM rear system with RedTek now, which can be even lower with some more work. I then asked Small Car "What about your system with RedTek?"... They said "Red what???". Again, not impressed and I'd like to hear differently.
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djsixbillion
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PostPosted: Mon Jul 18, 2016 7:50 am    Post subject: Re: Dual A/C System Planning Reply with quote

ThankYouJerry wrote:
Have you discussed your plan with Small Car? I did. They told me "Front, rear, but not both with my 1.8T." I'd like to hear differently. They also told me the best they've seen at the vent with their front AC system is 55F. Not impressed at all. I currently have 42F at the vent with the OEM rear system with RedTek now, which can be even lower with some more work. I then asked Small Car "What about your system with RedTek?"... They said "Red what???". Again, not impressed and I'd like to hear differently.


55F would definitely be disconcerting, though some here seem to have done much better. 40F vent temps reported here:

http://www.thesamba.com/vw/forum/viewtopic.php?t=5...p;start=80

Also not impressed with Small Car's support. I did ask them about my plans for a dual system and got a one-sentence reply: "yes it can be done, but we've never done it before".
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PostPosted: Mon Jul 18, 2016 9:44 am    Post subject: Re: Dual A/C System Planning Reply with quote

Again, go here and deeply consider what iulian did......

http://www.thesamba.com/vw/forum/viewtopic.php?t=5...p;start=40

Or...... Buy a used air box, send it to me. I'm itching to try the UD-110 into the stock box!

Pay for parts...... Lets see what we can create.

Dave
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Howesight
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PostPosted: Mon Jul 18, 2016 5:39 pm    Post subject: Re: Dual A/C System Planning Reply with quote

Regarding vent temps, 55F is not impressive, but in fairness to both Vintage Air and Small Car, that may simply be a function of how the thermostat is set up or how the compressor cycling on and off is set up. It may also be the case that the TXV sensor bulb should be re-located or adjusted to allow lower vent temps.

That Vintage Air system has the capacity to produce much colder vent temps. The tweaks above, plus careful adjustment of refrigerant quantity can get you there - - unless you insist on using the VW factory condenser. If so, all bets are off because it is an antiquated design that is also poorly implemented on the Vanagon (ie huge hole in the centre plus no sealing to the rad to enable rad fan draw-through).

Looking at the OP's schematic, the system shown in that schematic would benefit greatly from using a solenoid valve at the T-junction to cut high pressure refrigerant flow to the rear evaporator as needed. The solenoid would then be powered by the wire that used to power the compressor clutch, so that the rear evaporator is thermostatically controlled.

This configuration makes the front evaporator the primary one and the rear evaporator the secondary one. This makes sense since the driver is always present when AC is in use. It is worth considering using an orifice-tube restrictor in the front evaporator in place of the TXV so that when both front and rear systems are in use, the priority is given to the front evaporator. It will, however, work with a TXV in the front evaporator.

The capacity of the system is not going to be limited by your existing compressor, unless it is worn. Rather, the limit to total cooling capacity will be decided by the size and efficiency of your condenser. Even that can be improved by a well-executed rad fan system. If you space the radiator back (at both the top and the bottom) by, say, 1.0 to 1.5 inches, then you will have enough space to go to an even larger aftermarket condenser than the standard 16 x 24 inch unit most use as a parallel flow upgrade.

Lastly, I would not expect any licensed tech to install Red Tek. I believe it is a vastly superior product to R134A, but to use it, you need to install it yourself or bribe a tech to risk his livelihood.
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PostPosted: Mon Jul 18, 2016 10:42 pm    Post subject: Re: Dual A/C System Planning Reply with quote

My a/c tech installed RedTek for me after researching it and speaking with RedTek directly. RedTek is recyclable with r134a without contamination.
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PostPosted: Tue Jul 19, 2016 5:51 am    Post subject: Re: Dual A/C System Planning Reply with quote

Howesight wrote:


Looking at the OP's schematic, the system shown in that schematic would benefit greatly from using a solenoid valve at the T-junction to cut high pressure refrigerant flow to the rear evaporator as needed. The solenoid would then be powered by the wire that used to power the compressor clutch, so that the rear evaporator is thermostatically controlled.

This configuration makes the front evaporator the primary one and the rear evaporator the secondary one. This makes sense since the driver is always present when AC is in use. It is worth considering using an orifice-tube restrictor in the front evaporator in place of the TXV so that when both front and rear systems are in use, the priority is given to the front evaporator. It will, however, work with a TXV in the front evaporator.



Funny you bring this up about the zone valve. I purchased one from Nostalgic Air exactly for this purpose, to feed all the cooling capacity to the front when the rear unit is not turned on.

I do wonder though, does not the mere fact that the rear unit is off stop refrigerant from flowing through or will it simply ice up without any fan action?

I think I know the answer, the TVX valve is mechanical, it will be open if it senses a warm pipe so the unit will most likely ice up without a zone Valve.

I plan on wiring the zone valve to click on when the rear unit is turned on at the dash. The valve will be just after the reciever dryer past the "T" on the hose to the rear evaporator.

The front zone will always have refrigerant flowing though it when any zone calls for coolin. If the cold is excessive out of the Dash Vents (yeah, whoever made THAT statement about a Vanagon?!?! ) I will be able to mediate that by mixing in some heat.

Things to do, SO many things to do......

Dave
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PostPosted: Tue Jul 19, 2016 8:28 am    Post subject: Re: Dual A/C System Planning Reply with quote

Good call on the solenoid valve. I had thought about that as well, but wasn't sure if it was necessary. I also like Howesight's idea of triggering the solenoid via the rear evaporator thermo switch, but wondering if that might cause too much cycling. Just having it triggered from the rear AC "on" signal seems simpler and like it would work as well.
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PostPosted: Tue Jul 19, 2016 5:17 pm    Post subject: Re: Dual A/C System Planning Reply with quote

I looked on the NACP website and could not locate the refrigerant valve DJKeev refers to. Red Dot is a company that makes all kinds of vehicle refrigeration parts and systems (oriented to heavy equipment, trucks, industrial, etc) and their refrigerant valve is sold through many industrial supply houses at $85 or on Amazon for less:

https://www.amazon.com/Red-Dot-Refrigerant-Solenoid-71R9002/dp/B0028LAPN6
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PostPosted: Tue Jul 19, 2016 5:32 pm    Post subject: Re: Dual A/C System Planning Reply with quote

djsixbillion wrote:
Good call on the solenoid valve. I had thought about that as well, but wasn't sure if it was necessary. I also like Howesight's idea of triggering the solenoid via the rear evaporator thermo switch, but wondering if that might cause too much cycling. Just having it triggered from the rear AC "on" signal seems simpler and like it would work as well.


We may not be understanding each other. The rear AC "on" signal is the compressor-on signal. The factory Vanagon AC system cycles the compressor on and off depending on the thermostat setting and the anti-freeze up logic (which rarely comes into play due to the proper operation of the TXV). Since the front AC system will be on many times when you do not want or need the rear evaporator to cool, the compressor will already be running. The refrigerant solenoid valve that controls refrigerant flow to the rear evaporator only needs the signal that used to go to the compressor clutch to instead be connected to the refrigerant solenoid valve to open the flow of high-pressure refrigerant to the rear evaporator core.

On the factory Vanagon AC system, when the "AC is switched on", the compressor may or may not be switched on also, but the evaporator fan switch is energized and the rad fan runs at low speed, regardless whether the compressor clutch is engaged. The compressor clutch is only energized (ie: "switched on") when the "amplifier" decides, based on the evaporator temperature sensor and the setting of the AC temperature knob, that the compressor needs to run.
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PostPosted: Tue Jul 19, 2016 7:04 pm    Post subject: Re: Dual A/C System Planning Reply with quote

I ordered that valve on March 26, 2016, $39
Description. 12v Freon Shut-Off Valve 119-9928

I guess they no longer carry it?

Dave
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djsixbillion
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PostPosted: Wed Jul 20, 2016 8:51 am    Post subject: Re: Dual A/C System Planning Reply with quote

Howesight wrote:
djsixbillion wrote:
Good call on the solenoid valve. I had thought about that as well, but wasn't sure if it was necessary. I also like Howesight's idea of triggering the solenoid via the rear evaporator thermo switch, but wondering if that might cause too much cycling. Just having it triggered from the rear AC "on" signal seems simpler and like it would work as well.


We may not be understanding each other. The rear AC "on" signal is the compressor-on signal. The factory Vanagon AC system cycles the compressor on and off depending on the thermostat setting and the anti-freeze up logic (which rarely comes into play due to the proper operation of the TXV). Since the front AC system will be on many times when you do not want or need the rear evaporator to cool, the compressor will already be running. The refrigerant solenoid valve that controls refrigerant flow to the rear evaporator only needs the signal that used to go to the compressor clutch to instead be connected to the refrigerant solenoid valve to open the flow of high-pressure refrigerant to the rear evaporator core.

On the factory Vanagon AC system, when the "AC is switched on", the compressor may or may not be switched on also, but the evaporator fan switch is energized and the rad fan runs at low speed, regardless whether the compressor clutch is engaged. The compressor clutch is only energized (ie: "switched on") when the "amplifier" decides, based on the evaporator temperature sensor and the setting of the AC temperature knob, that the compressor needs to run.


I think we're on the same page - the compressor clutch signal from the front Vintage Air system will tie in to stock Vanagon AC relay, downstream of the Vanagon thermostat switch. The output of that switch would then tie directly to the refrigerant solenoid valve. I'll try to mark up the wiring diagram that I posted earlier to show this, but operation should be in this fashion:

*Front system in use only - turning the Vintage Air temp control to cold will trigger the compressor on, which will then cycle based on the front evap thermo switch, AS WELL AS the stock Vanagon trinary switch. The low speed radiator fan should also be engaged. Flow of refrigerant to the rear evap is blocked by the normally-closed solenoid valve (that Red Dot valve seems to be a good option - found it here for about $50 - http://www.partdeal.com/red-dot-liquid-line-refrig...-0p.html).

*Front and rear system in use - switching on the stock rear Vanagon AC system will now energize the solenoid valve, allowing refrigerant to flow to the rear evap, along with energizing the rear evap fan. Compressor cycling will still be controlled primarily by the front evap thermostat setting.

Does this sound about right?

djkeev - sorry but a local buddy has first dibs on the stock heater box! I may indeed live to regret giving up the fresh air, but it doesn't seem that difficult to add an inlet to the Vintage Air box. A modification I may make down the road.
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PostPosted: Wed Jul 20, 2016 3:53 pm    Post subject: Re: Dual A/C System Planning Reply with quote

Photo of my 12v Nostalgic Air refrigerant flow cut off valve.......

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Dave
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