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Thread: RPGs air conditioning build

  1. #1
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    RPGs air conditioning build

    Installing a Vintage Air heating and air conditioning system in an 818S.

    I’m over half way through installing a Vintage Air heating and air conditioning unit in my 818S, and think the hardest parts are done (hoses and electrical), so I thought it might be helpful to share my experience on the forum. This is my first car build and my first air conditioning build, so it’s offered only as one way to do it. It’s probably not the best, cheapest, or most elegant way, and some things may need to be corrected, but it seems to be working for me.

    I am indebted to AZPete, the pioneer of 818 air conditioning, for sharing his document regarding the installation of an earlier version, and to Lsfourwheeler for his arrangement of controls and louvers in the dash, which I am shamelessly copying. There are many other good references to AC installs in other build threads, many of which I have read in the past and appreciated the helpful information, but they are too numerous and hard to find again to acknowledge specifically. AZPete has a pdf description of his installation which I highly recommend requesting from him and reading. Lsfourwheeler’s air conditioning build can be seen at https://www.818coupe.com/the-build/air-conditioning/.

    Note: My design uses a 2006 Impreza NA donor. It may need adjusting for other donors, especially the electrical wiring. This information represents my progress to date. I have not installed the dash with louvers and controls, or charged and tested the system yet. I’ll add more information and photos as I complete those tasks.

    The first question one might ask is why on earth should I put heat and AC in an open 818S roadster. The benefits in an 818C are obvious, and in an 818R are dubious. After polling my friends and acquaintances that have convertibles or know someone who does, they universally admitted running the AC with the top down when it was hot outside, or the heat when it was cool. It also seemed best to install it during the build just in case I added a soft top later. I didn’t opt for a defroster, as I don’t think it’s needed with an open roadster.

    Going with a Vintage Air Mini Gen II was an easy call given the experience of others and the apparent absence of a simple alternative. To hold down costs, I decided to use the donor’s compressor and condenser, and to mount the evaporator under the dash without modifying the frame. Before starting, I borrowed an evaporator mockup from my local Vintage Air distributor, Raleigh Speed Shop, to verify the fit. There is some intrusion into the passenger’s footwell from the unit, and some more from the hoses, but it leaves plenty of room for their feet.

    AC mockup 1.jpg

    The evaporator doesn’t show much once the dash is in place.

    AC mockup 2.jpg

    Next came the donor compressor install. Mine needed a new idler pulley and hardware plus a new fan belt. Installation would have been much easier if I hadn’t removed the compressor in the first place, but it was pretty easy nonetheless.

    Compressor install.jpg

  2. #2
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    Installing the condenser required making brackets to both hold it close to the radiator and prevent it from sliding down the surface of the radiator. These took some time to design, as I tried to accomplish both with a single bracket on each top corner. Once I realized that each top corner just needed two simple tension brackets, making them turned out to be pretty simple. They attach to the condenser with small screws and nuts and to the radiator mounts, and hold the condenser firmly in place.

    Here are the brackets after painting.

    Condenser brackets.jpg

    Here are the top left and top right brackets.

    Top left brackets.jpg
    Top right brackets.jpg

    Here’s the other side of the bracket that runs under the dryer and the bottom right bracket.

    Under dryer bracket.jpg
    Bottom right bracket.jpg

    Mounting the evaporator was fairly straightforward. I placed it about as far as it would go to the left and toward the firewall and tied it in place with cord. The mounting bracket on the right connected directly to the frame, and the two straps were bent 90 degrees at the top and bolted to the nearby frame. Unfortunately, while the right side had a hard mounting point, the left side was dangling from the two straps, free to move front to back. A small bracket on top fixed that.

    Evaporator install.jpg

  3. #3
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    The cooling hoses were the most challenging part of the install. Since the dryer is attached directly to the condenser, only 3 hoses were needed: the liquid hose from the condenser to the evaporator, the suction hose from the evaporator to the compressor, and the discharge hose from the compressor to the condenser. Like AZPete, I chose to use the donor hose ends to connect to the compressor and in my case the condenser as well. Raleigh Speed Shop, who has done lots of Vintage AC installs, did a great job of welding together my donor ends and adding standard hose fittings. We also added a straight connection in each hose to avoid a hose alignment issue, given that the hoses don’t want to twist. Here’s a diagram of my hoses and fittings.

    818 Hose drawings AutoACfittings.jpg

    At the condenser, both of the donor tubes interfered with the upper radiator mounting bar, that frame piece with the holes in it. The photo below shows the donor parts connected to the evaporator and the mounting bar angled away. That needed fixing.

    Condenser tubes.jpg

    For the liquid hose, a slight bend near the condenser solved that problem. To make the bend, I cut a square groove in a wooden cylinder using a lathe, and bent the tube in the groove. The tight fitting groove kept the tube from collapsing.

    Tube bender 1.jpg
    Tube bender 2.jpg

    I also kept the switch port for a new trinary switch. On the evaporator end of the tube, RSS welded on a straight connector to go to the liquid hose.

    Condenser liquid line bend.jpg

    The discharge hose at the condenser interfered as well, so I cut the end off, cut another 3/8” of the tube off, and had RSS weld it back together about 180 degrees from the original. It also got a straight hose connector on the end.

    Condenser tubes clear bar.jpg

  4. #4
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    At the compressor, the discharge tube and valve just needed a straight connector. The suction tube needed a valve and straight connector. I used the valve from the other end of the hose and had the 3 parts welded together. Had I planned better, the suction valve wouldn’t be right under a frame piece, but I think there’s room for an angled adapter.

    Compressor tubes.jpg

    The evaporator was the easiest, needing only an elbow to hose fitting for the liquid and suction lines, which went directly toward and through the firewall. Grommets sealed the holes. The suction hose elbow must be insulated to avoid condensation, but isn’t shown in this photo.

    Evaporator hoses.jpg

    I wanted to run the suction and discharge hoses through the tight front corner with the big coolant tube on the driver’s side. To give me as much room as possible, I decided on reduced size hoses and fittings. I also chose beadlock style fittings rather than the E-Z Clip style because Raleigh Speed Shop could also do the crimping. The beadlock fittings were substantially less expensive than the E-Z Clip fittings as well.

    Next I measured the hose lengths and ordered the fittings and the low leakage reduced size hose from autoacfittings.com. They had everything I needed and a pretty simple web site for ordering. Once they came in, I had all the tubes welded and one end crimped onto each hose. I then selected the routing and tie down points for each hose, held my breath, and cut them to length. Next each hose got its other end crimped on.

    Being warned by RSS, I saw that the O rings from Vintage Air were substantially thinner than the ones used by Subaru where the tubes fit into the condenser and compressor. I bought Subaru O rings for those connections. After connecting the 3 hoses, they actually fit nicely.

    Here are the final lengths for each hose without and with the fittings on the ends:
    Liquid, 31.5” / 34.5”
    Discharge, 120”, 125”
    Suction, 134”, 138”
    Your length, of course, will vary based on your routing and attachment tubes.

    The driver’s side now has the coolant return tube, the ac suction and discharge hoses, the shifter cables, and the overflow hose in close proximity. I didn’t want the coolant heat to leak into the ac hoses, but did want any heat from either to escape into the air if possible. Rather than insulating the tube and hoses, I used the shifter cables and overflow hose to separate them and I’m hoping for the best.

    AC hose routing.jpg

  5. #5
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    Next came the heater hoses which ran down the passenger side through that same tight corner.

    Heater hose routing.jpg

    I chose to use elbows at the evaporator to point the hoses straight through the firewall. There was just enough room to install the heater control valve inside.

    Heater control valve.jpg

    My Subaru engine needs coolant flowing all the time through the heater hoses. FFR supplies a U shaped hose to connect the heater pipes at the engine. The Vintage Air heater blocks that flow when not heating, so a bypass is needed. Vintage sells an H shaped bypass that lets some or all of the coolant bypass the heater. To allow coolant to bypass the heater except when I wanted all the heat, I installed a mechanical bypass valve in an H configuration above the transmission. To control the bypass valve remotely, I attached a door lock actuator. Initially it will be controlled with a rocker switch, but I hope to automate it later.

    Bypass.jpg

    The final hose is a drain hose from the bottom of the unit through the firewall and down to drip onto the ground. That was easy enough, although the hose didn’t want to stay round.

    Drain hose.jpg

    For the controls and louvers, I plan to copy the design of Lawson Sumner (lsfourwheeler) with four louvers and controls in the middle of the dashboard. Here’s his photo.

    Dashboard.jpg

  6. #6
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    Wiring the Vintage Air system was harder than I expected for several reasons. First, I cut all the donor HVAC wires at the ECM, expecting the AC to be an independent system, and had to rerun 3 of them after I had laced up my wiring. Second, I wanted to use the ECM features that turn off the compressor during wide open throttle and raise the idle speed when the compressor is turned on and I couldn’t find a wiring diagram explaining how to do it. I also wanted both radiator fans to come on when the liquid line pressure got high enough to turn on the trinary switch. Another hurdle for me, which I haven’t solved yet, is automatically controlling a heater bypass valve.

    To get started, the relays and circuit breaker were mounted as shown below, and I used the ABS power wire (WR, 30A fuse) for the main power and the airbag system power (Red, 5A fuse) for the ignition switched power. I used ¼-28 bolts into threaded holes in the frame for grounds as I found the installation process easier than using rivnuts. I also measured slightly lower resistance for them compared to ¼” rivnuts, although either ground technique is good enough. If I were to do it again, I’d mount the relays and circuit breaker to the frame in front of the evaporator so I didn’t have to lengthen any of the wires.

    AC wiring relays.jpg

    The ECM Wide Open Throttle function that disables the compressor during WOT, giving you all the power you can get from the engine and perhaps preventing the compressor from over-reving, requires some wiring modifications to work with the Vintage Air system. These mods also enable the engine idle control that raises the idle speed when the compressor is on. I’ve redrawn the Vintage Air wiring diagram to show the switch logic more clearly and to add the needed modifications.

    AC schematic.jpg

    The 2006 ECM grounds its Pin C9 to close the compressor relay and turn the compressor on. It does so when its pin B16 is grounded, meaning that the donor blower has been turned on, and its pin C23 is 12v, meaning that the blower and AC are turned on and the evaporator temperature is above 33 degrees. That is, unless the throttle is wide open or perhaps the engine revs are too high, in which case the compressor is turned back off. Since the ECM doesn’t do much when just the blower is turned on when it’s not connected to the donor, pin B16 can be permanently grounded. Pin C23 can be connected to the output of the Vintage thermostat to make it 12v when the compressor needs to be turned on. However, it may not reliably go to ground when the thermostat switch opens and then the compressor switch opens. Adding a 10k ohm pull down resistor to pin C23 fixes that.

    Now ECM pin C9 will go to ground to turn the compressor on, but the compressor needs a 12v signal to turn on. Adding a relay between the Vintage thermostat and the trinary switch as shown corrects that issue. So would retaining and rewiring the donor compressor relay, but I couldn’t find mine. Now that the ECM is getting the right signals on C23 and B16, the idle control should work properly.

    Another desirable feature is having both of the radiator fans turn on high to pull air through the condenser whenever the refrigerant pressure gets above 250 psi, but still allowing the ECM to turn the Main fan on first and then later the Sub fan based on engine temperature. This requires connecting the ECM outputs through diodes to the trinary switch as shown in the above schematic.

  7. #7
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    The remaining work for me is installing the louvers and controls in the dashboard, connecting the louvers to the evaporator, extending the heater vents beyond the tunnel side panels, replacing the dryer, evacuating and charging the system with HFC-134a and oil, and testing it. I hope to end up with a system that works as well as others have reported.

    The following is a list of the parts bought so far for the heating and AC system. The prices are approximate, and some don’t include tax or shipping. Tube welding ran $220, and crimping $80. All in, I’m at $1050 so far, with charging the system the largest remaining anticipated cost.

    Parts list 1.jpg
    Parts list 2.jpg

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    This information is very useful, so thank you for posting.

    I happen to be working on the A/C part of my build as well. The one thing I was stuck on was fittings and hoses, and your information helps me a lot

    I however chose a different route and used and electric compressor.
    A lot of people dislike electric ac compressors because they don't product that much btu, but I figured it would be okay for a small coupe.
    This way I don't have to run long hoses from the back to the front and most A/C components stay ahead of the front firewall - compressor, inverter, battery, condenser, with evaporator being under the dash.
    This also means that I didn't have to use the compressor ECU controls. One thing to note is that I did have to upgrade my alternator to the outback H6 one to support this compressor.

  9. #9
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    Thanks Neeraj, I'm glad you found it helpful. The electric compressor is an interesting alternative. It does simplify things. Which one are you using? My 06 donor AC system was 5300 watts, but with a mini evaporator in the 818, it may not be able to use all the compressor capacity.

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    The compressor I am using I got off AliExpress from China. There's a lot of them on there, but shipping can increase the costs significantly. It is rated up to 3000W, which would be 250A @ 12V. That would be some really thick wire, and my alternator gives 110A. So I'm planning on running it lower than that.
    My evaporator is also Chinese, combo heat A/C unit. Not as compact as the vintage air unit but it fits with dash tube modification.

  11. #11
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    Thanks for sharing those details, Neeraj. It will be interesting to see how your install works out. It may be easier than you are thinking.

    In A/C systems, cooling capacity is rated in watts, which is the rate at which the unit will extract heat from a space. Fortunately it only takes about a third of a watt of electric power for a watt of cooling capacity. I suspect your compressor rating of 3000 watts is cooling capacity, so it will only need around 1000 watts of electric power, or around 80 amps. That means that your H6 alternator should handle it as long as the engine rpm is around 1200 or higher. If you sit still in traffic a lot, you may want to consider tricking the ECM into raising the idle speed when the compressor is on.

    I think 3000 watts should be plenty to keep an 818 coupe cool. Best of luck with your install.
    RPG

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    I think you would be correct normally, however in this case I think the power draw is 3000W. Take a look at the attached photo - screenshot of the product I ordered.
    It might be a little overkill.
    https://photos.app.goo.gl/SXiS9TNepVTwTpus7

  13. #13
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    You're absolutely right Neeraj, I guessed wrong. That's a LOT of power. How do you select the speed? The lowest setting is 120 amps, so it will use up everything the alternator is putting out and pull any extra amps from your battery while it's running. You're right, you'll need thick wires. I look forward to hearing how this works out.
    RPG

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    Well I looked into it and I still have no idea how to control the speed.
    I found a pinout of the inverter I'm using and it seems to have a pressure switch input (do i need low and high side?), an "evaporator signal feedback wire" (i'm thinking green wire from my evap?), and an "evaporator thermostat wire" (? brown wire from thermostat?)
    Screenshot 2021-11-11 165216.png
    Although as far as I'm aware my inverter is rated up to 1200W. Don't know what will happen if the compressor pulls more than that.
    Almost seems as I bought a compressor made for a bus. Maybe I run 2 alternators? Or buy one of those really beefy 280amp ones the sound guys use.

  15. #15
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    Looking into speed control, I searched using your compressor image and found 2 other web sites selling an air conditioning compressor using the same photo.

    https://www.alibaba.com/showroom/bus...ompressor.html 10th item down on the page.
    https://en.aliradar.com/item/1005002...hicles-24V-48V

    It appears the 3 speeds result from using 12V, 24V, or 48V, so that’s easy. It also appears that the compressor has a permanent-magnet synchronous motor (PMSM), which is a good thing. That means it needs a controller to convert the 12V DC power into alternating current (AC) power, starting at a low frequency to get the motor started and building up in frequency until the motor is turning at 3000 rpm.

    It sounds like your controller, or inverter, must also control whether the compressor is on or off. The pressure switch is on the liquid line and opens a switch between 2 wires if the pressure is too high and may burst things, or too low and may starve the compressor of oil. You’ll need to know how to connect those 2 wires, but it may be to the 2 pressure switch inputs. The controller will also turn off the compressor if the evaporator coil gets to 32 degrees so it doesn’t freeze up. That’s probably the "evaporator signal feedback wire" from your evaporator. The controller should also turn the compressor off if the cabin temperature is below the thermostat setting. That’s probably your "evaporator thermostat wire".

    I’m doing some guessing here, and as you know, sometimes I guess wrong. Do you have any more documentation about how to hook the controller up?

    If the controller can only handle 1200 watts and the compressor needs 1450 watts to spin at 3000 rpm, the controller will reach its maximum power before the compressor reaches 3000 rpm. If it’s a good controller, when it reaches 1200 watts, it will stop raising the output frequency and the compressor will spin at something less than 3000 rpm. That should be ok, as it will just stay on longer, or not cool quite as much.

    Your electric compressor project is a little more complicated than I expected, Neeraj. I’m glad you’re tackling it and hope you’ll share your results when you’re done. Best of luck.
    RPG

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