T3--Under dash aftermarket AC unit review//install

[Piledriver]

Hydraulic crimper made for purpose, you can also get a screw operated frame that uses same die, but for what the local shops wanted to do all the crimps (and the PITA that entails) I bought a hand pumped hydraulic, sniped at a decent price, has full set of die for std and reduced barrier hose. I was able to set the fitting orientations after the hose was clamped down and do the crimps in place.

Chinese, indistinguishable from the (Chinese made) Mastercool set.
(possibly 4th shift production, really good copy in any case)

Could probably do many sizes of hydraulic hose as well.

Can get the die IDs if you like, the design is ~identical to a lot of crimpers, segmented die floating on a silicone substrate, keeps the 3 sections of each half together.

[Piledriver]

After just over 4 years ( ) I finally have cold air.
The under dash unit has been doing duty as a fan summer and winter, in winter it blows around the output of the BN4.
I'll have to add a "heat/cool" switch so I can keep using it that way.

Was blowing cold after one 12oz can of 134a, the variable displacement compressor is an interesting beast.
(took 36 oz, which was about exactly what was calculated, the 12x14 condenser seems sufficient, will be tested well the coming week, a std size condenser would have swallowed another can of 134a)

Used 4 oz. PAO 68 oil, all in the compressor where it will probably stay, as it doesn't really mix with 134a.

Still have to make clean on the wiring and finish a few details, add a fuse for the condenser fan, but it all seems to be behaving as expected.

The 130W 10" Maradyne fan moves a LOT of air. (M103K)
(It has a dedicated 12ga line straight from the battery, draws ~8A by itself)
Bent/welded up a shallow aluminum plenum for it so it sucks on the whole condenser.
Still need to fab the wheel well liner/splash guard.

Trinary switch works the fan relay and routes the signal for the compressor clutch as designed, had a spare relay on my MS ecu mount plate that finally got used for the compressor clutch. Ran the control line via a 12 wire shielded signal cable that currently terminates in the trunk to later hook up other stuff to the ECU.

The compressor doesn't seem to disturb the idle significantly when it cycles, but I should probably add the jumper wire to make the MS3 aware of the AC compressors clutch state.

Ran the hoses down the center of the tunnel underneath, and up the middle of the front as you can ~only do on a T3.
Will be adding a skidplate up front for a little more protection for the AC and fuel line/pump/sump etc.

[doc]

Could we see some pics please? Especially before you start to really close things up.

doc

[Piledriver]

Ok, though i had it well covered already but here's a few more pics of the hose routing details.
(3 max upload per post)

condensor-fan-airbox.JPG

front-low-side-hose-route.JPG

high-pressure-front-torsion.JPG

[Piledriver]

3 more: Ask if you want pics of something specific.

lines_front-1.jpg

lines_underneath.jpg

lines-rear_torsion.JPG

[Piledriver]

Ended up needing to recover some of the charge, was overcharged (easy to do on the variable displacement compressors), was initially concerned that the condenser was too small but its working absolutely splendidly with ~12 oz less freon.
(weighed it in and out, allowing 4oz for the manifold lines etc)

The condenser and subsequent high pressure fluid lines take up most of the freon when the system is running, and even with the long suction and HP lines from the back of the car it only really needed ~24 oz.
The condenser I used was quite small, and the liquid line to the evap is relatively short and straight.

The HHR system the compressor came from only needs 15oz, and has a slightly larger condenser, but my fluid lines are and reciever/dryer are larger/longer, so its a "sane" charge of freon.
(There has GOT to be a better way to simply calculate the charge on a custom system like this, my subcooling is sane at least set on max flow with the doors etc wide open, only ~+12-15F above ambient with max heat load, about as good as you're going to get on a car)

Used 12x14 high efficiency parallel plate type condenser (~12x11" effective fin area) and killer 10" fan and ductwork, doesn't even run all the time now at 98F OAT, at least with the doors closed and the car interior cooled down. (am using a somewhat unconventional configuration with the variable displacement compressor and a TXV: The TXV and in-dash thermostat are effectively the low side control in this case.

Still concerned about too little freon and low lubrication, but running PAO oil it tends to stay in the compressor.
Was trying to err a little on the high side and was too successful.

I ended up just recovering enough so the low side was correct for the OAT on the 134a temp/pressure chart, just in control range of the VDC control valve it ends up ~30 PSI.

The only "bug" in the system is the temp control on the under dash unit mix/max temp are labeled backwards...

[Steve Arndt]

What is your high pressure when you see 30 psi on the low side gauge? Just curious.

I want to put a/c in my baja bug. I don't know a thing about the variable displacement compressors. How do they work and control themselves?

[Piledriver]

What is your high pressure when you see 30 psi on the low side gauge? Just curious.

I want to put a/c in my baja bug. I don't know a thing about the variable displacement compressors. How do they work and control themselves?

I should note I selected this specific compressor because it was:
A) Cheap and very common, and is still used to date, most modern design available.
B) It FIT.
It's kinda long and skinny and has a smallish pulley.

I also have a Sanden like everyone uses on everything and it wouldn't fit where I needed it to go in a T3 without extensive body hacking/welding. All I needed to do for this one was stretch a small area with a palm nailer to clear the manifold.
(I DID have to weld up a custom manifold and mount as unlike the Sandens there aren't 200 aftermarket adapters for sale)

High side depends on the outside temps, as well as the compressor stroke, which is all about the pressure it sees on the low side.

I have some good bookmarks..:
http://delphi.com/docs/default-source/o ... f?sfvrsn=0
Just the SAE paper from Delphi.

I had a bookmark where a fellow explained it in smaller words somewhere
This looks like it, post by ACProf
http://acsource.net/acforum/viewtopic.php?f=1&t=9447

The vast majority of the older gen VDCs are used with an orifice tube setup, although Delphi and GM and Mercedes (possibly Delphi AC?) have released units with TXVs and clutches as well. (possibly even the HHR, as it has a clutch and a non-electronic control valve.)

More recent ones use fully electronic controls for the displacement and clutch, but it looks like it would be possible to control with a MS3s programmable IO (PWM), and if all else fails, if you plug the control valve (or perhaps unplug the connector) most will usually run at full stroke and work like a std compressor.(if it has a clutch)

Many of the earlier units are clutchless, and run full time, so either a pressure based control valve or electronic control are required to change the displacement. (control range is ~5-100% displacement)

I'm using one from a 2011 HHR that got rear ended hard w/10K miles. $65, shipped.
Has clutch and pressure based control valve, is a Delphi V7. Electronic valves were also used on some apps.

I should also note the condenser fan is operated only by the trinary valve (high side pressure), so if the pressure is under the setpoint cruising down the road just from ram air, it doesn't run and suck 10A continuously.

(It actually was cycling off occasionally running it in the driveway today once the cabin cooled off, ~96F out and very high humidity, so I guess the tiny condenser is truly big enough (with the mongo fan, at least)

The cabin temp to vent temp delta was ~45-50F, which is just peachy. (full load/doors open/heat soaked car etc)

I should monitor the condenser fan when cruising at various speeds, the intake hole is ~the area of 2 playing cards, fully hidden behind and slightly below the top of the bumper... Almost invisible unless you are under the car.

[raygreenwood]

Piledriver.....how are you controlling the variable displacement function? Shat type of signal does it require?
Ray

[Piledriver]

Piledriver.....how are you controlling the variable displacement function? Shat type of signal does it require?
Ray

I'm not.

The expansion valve controls lowside pressure, the thermostat runs the clutch, so the variable displacement is effectively ~inoperative under most conditions, other than greatly softening the hit of clutch engagement.
(the V7s destroke to min when off, so it has a mechanical soft start, likely was the main point for default to min stroke)

On a orifice tube AC configuration, it would be controlling displacement entirely via the lowside pressure.
(orifice tube==fixed restriction)

if it had the electric version of the control valve its PWM controlled, 12v dumb solenoid, ~100hz would probably work fine.
I might have to pick one up to play with to give it a "soft start" and an electric thermostat via PWM etc.

This unit also has a clutch, which draws surprisingly little current, running it via 20ga wire.
It will be Megasquirt controlled so I can cut it out at high loads, or if the CLT gets too high etc.

[raygreenwood]

I have been looking at these from afar and wondering what the baseline signal type was for the stroke control......and wondering if range of control could be operated by something simple like a potentiometer.

Not looking so much for full infinite variability.....just to be able to adjust from the dash to reduce load for driving conditions.

To me this means that when the cabin and the evaporator system are already cooled down...and say I pull into light to light traffic....I could drop it down to say 10-15% just for chill maintenance. Medium speeds I might leave it up medium high. High rpm highway speeds with a lot of air moving over the condensor I might run it at 5-10%. Ray

[Piledriver]

The original setup used on the HHR/Cobalt etc does just that, on my setup with an expansion valve it works mostly like a typical AC system.

It works either way, the thermostat in the under dash bit cycles the compressor clutch at whatever temp you like.
With the original setup you get the best of both.

[raygreenwood]

I was thinking that if the stroke controller bleed valve is simply current controlled instead of a generated electronic signal.....I could just control it manually by, setting....and as you noted have the normal expansion valve kick the clutch out when predetermined maximum cool is, reached. ....which would come in handy at constant highway speeds.

Otherwise I would like to in general keep the clutch engaged constant while I have it on.....constant load with no cut outs during low speed light to light operation.

I am probably 8 mos from the do or die decision about installing ac or not in the 412. For the most part I don't cars about ac in my 412......but its superior for driving in wet weather with the windows rolled up for defogging.

The two biggest items for me were really liking the variable stroke compressor ......and hopefully finding a compressor with the correct rotation.

I am planning a bracket build that will keep the compressor weight and tension from handing on the cooling manifold. It will have 3.5 feet of extra line snaked around the engine compartment in a hanger loop.

When I need to get to everything on the 3/4 side of the engine compartment. ....I will pull a pivot bolt and a lock bolt, slip the belt off....pull the compressor out of the engine compartment on its extra 3.5 feet of hoses.....and have a rod that mounts in a socket on the bumper overrider to part the compressor out of the way....without disconnecting lines....while I work.

The rigid lines would run up the C pillars under the padding.......to a ceiling mounted air and fan box....like in a van. Condensor hard lines down the B pillars, up the outside of the heater channels to a dual condensor on each side below the headlights. Been working out the design for a long time.

If I can find a compressor with electric stroke control and correct rotation...im halfway there. Ray

[Piledriver]

Note I am running this on a T4 in the usual T4 config (but on a Vanagon shroud), so the compressor is rotating backwards from its original app... No weight on the intake or exhaust, all hangs off the shroud.
The T4 cooling setup was designed with AC in mind.

Get one with the electronic control valve and you can PWM it any way you like.
I would also get the clutch as a safety for running at low temps.

Piston compressors don't care which way they turn, they have reed valves and blow and suck the same.
The clutch has some bits that look like they would prefer to be under tension, but the York compressor off my 914 was designed the same way and probably drew 20HP, and it didn't matter then either.

I'm pretty certain you can score a v-belt clutch pulley for it too, I'm running a 4 rib serp belt with a slightly modified Ford PS pulley on the crank, the bracket has a jackscrew w/locknut to set belt tension.
(loosen everything, set belt tension then lock down the bracket)

Both the compressor and the pulley are 5 rib now, but it didn't line up right, and with it only running the AC 4 rib seems quite sufficient, and lines up perfectly, just have to fiddle a bit with what groove it goes in on install.

I had to do a tiny bit of clearancing on the fan housing and block mounting standoff bits so the belt would clear with the larger than std T4 pulley. (see pics earlier in thread)

I was looking at reworking the clutch direction, but I strongly suspect it doesn't really care.

There's no need for the extra 3 foot service loop, just run the hoses down the engine compartment on the 3/4 side.
Might have to take off an Adel clamp or two, but once the engine is down, the compressor/lines will simply unbolt and can be hung as you described.

Leery of the overhead setup, the one in my Vanagon hit me in the head twice when it fell down, and that was a factory setup.
The under-dash evap setups are available in many configurations and looks, and could also easily go in the frunk with ductwork. (They have various front panels for the basic evap/blower setups, some with hose outlets for hidden installs)

[raygreenwood]

Very nice to know Pile!....I will back read to see what compressor you are using. I have also though about making the primary four shroud bolts 10mm....just to make sure load is no issue.

The overhead fan unit I am working with will probabaly use an evap unit from a mk 4....good and easy to come by.

The overhead unit I am designing will have welded tabs to sit on the internal rails under the headliner....bolted in place. The 412 is ideal for overhead....huge overhead space...rails/flanges to mount on.....and I have had underdasb units from the factory. There is too much under the dash that needs regular service to use them on this car. Ray