Re: Suburban A/C fix + Vintage Air?
 

Oh man, I can barely breath... My virtual finger are crossed for you.

Re: Suburban A/C fix + Vintage Air?
 

I would recommend drawing up a schematic of the wiring so when you come back to it in 3 years you can figure out what you did...
As an occasional buyer... It's a selling point to have a wiring diagram for any hot rod.
Even some custom shops will refuse to work on electrically modified vehicles without documentation because they have to create said documentation as they go so they can figure out what went wrong. That kind of work is time consuming and most people don't want to pay shop rate for that kind of tedious time consuming work.

Re: Suburban A/C fix + Vintage Air?
 

Also it helps remember what you did a month ago!
Here are all the changes I made to the system. Hatzie gives good advice.

https://photos.smugmug.com/VehiclesO..._diagram-M.jpg

I had to relocate my fuel pressure regulator which WAS where the AC is now. It took me an hour to figure out where to put it. At this point I realized I needed to just quit for the day.
I asked my 11 year old buddy for some advice. And I mounted it to the firewall.

Still need to

1. Run the inlet fuel line.
2. Run the wire for the rear fan
3. Vac the system for an hour
4. Hook up rear fan switch
5. Fire it up!

Re: Suburban A/C fix + Vintage Air?
 

I was being generous. My CRS is that bad at times but not all the time. Yet.:lol::lol::lol::lol:

Re: Suburban A/C fix + Vintage Air?
 

Per the manual the charge required for "Overhead System C-K" which I believe is GM speak for the rear system, is 5 lbs 4oz.

There are 15.3 fluid ounces in a pound, with means the ORIGINAL R12 requirement is (76.5 + 4 oz) = 80.5 oz.

My supplier (Mike) at Classic Auto Air says that R134a should be 70-80% of the original R12 charge.

Which translates to: 56.35 - 64.4 oz or R13a for this unit, or 6 12oz cans.

Mike said charging it should take a good 45 minutes. He mentioned adding 2lbs, then 1 oz at a time, watching the thermometers in the vents front and rear for "maximum chill".

It's been in the mid 80s all week, and now it's 65 degrees out!

Last run to the parts store to buy some "chilly juice" and IT'S ON!

https://photos.smugmug.com/VehiclesO...IMG_9726-M.jpg

Re: Suburban A/C fix + Vintage Air?
 

I've never had good results trying to extrapolate pounds of R12 to R134, HFC152, or R290/R600 blends.

I saved this method from some posts Jungle Eddy made about using hydrocarbon and other alternative refrigerants on a Fidonet Aircon message forum that I frequented on a dial in BBS system. Around 2001 or so. I thought it was older than that.
This method always gives me decent results no matter what refrigerant is used.

--------------
Posted by JungleEddy on September 05, 2001 at 08:17:44: via: or 66.25.151.188

More important stuff.

How to charge an A/C system.

Note: This method will work for any automobile A/C system regardless of refrigerant type. The pressures I list here will only be correct for HC’s.

I have been trying for the past couple of weeks to come up with a “system” that would allow just about anyone to properly charge their A/C system. While this method I have developed is not fool-proof, it yields the closest thing to a perfect charge I have found. I have tested it on three “non A/C” mechanics in the past few days with great success.
First: If you have not read my previous post on vacuum, flushing, oil supply, leaks and fans etc etc, please do so now. You still need a properly assembled system to get proper cooling!

This ENTIRE process makes a few IMPORTANT assumptions!!
1. The ambient air is OVER about 84 degs.
2. You have a set of A/C gauges
3. You do not take shortcuts.
4. You are able to read and comprehend enginsh.

This process will work down to about 80 degs ambient air, but will be MUCH MUCH easier to over charge below 85 degs ambient air!! Relative high side pressures will be lower at 80 degs ambient and pressure drop after wetting the condenser will be less dramatic.

Pull a hard vacuum for a minimum of 15 minutes, 60 minutes is perfect. Static charge the system to about 65 psi while the engine is NOT running.

If you have a low pressure cut out switch on your system you will need to adjust it down to 18-19 psi sometime during this process. Personally, I find it easiest to do this about midway (now) through the charging process. Remove the connector from the switch and turn the adjustor screw about 1 full turn counterclockwise from its factory position. (counterclockwise is less psi, clockwise is more psi, 99% of the time) Start the engine and turn on the A/C, recirc, max fan, and engine at idle. Max fan is important, since it will help keep the evaporator from freezing as you charge. Charge the system slowly (if you have to!) until the compressor stays on fairly continuously at IDLE. The adjustment I illustrated above should give you a cut out psi of 12-18 psi. Watch your low side gauge and SLOWLY increase engine rpm. The low side pressure will drop slowly but substantially because you are still undercharged. Watch it drop from 20+ psi down through the teens and carefully note where the compressor cuts out. Return the engine to idle and pull the connector to the cut out switch and adjust it accordingly. Try this several times until, as the engine is slowly revved the compressor cuts out at about 18-19 psi on the low side.

The Charge:
Bring the engine rpms up to a continuous 1200-1800 rpm. Begin to add refrigerant (if you have to) SLOWLY until you notice that the air at the vents is noticeably cooler than the ambient air, say at about 65-75 degs or so.
At this point grab your garden hose and hose down the condenser; soak it once only. Your pressures will drop dramatically. The high side should drop below 150 and the low side should drop low enough to cycle the compressor, or if the switch is temporarily “jumped” the low side should be well below 20 psi. I prefer at this stage to jump the connector to the pressure switch to keep the compressor running continuously. It makes the process go much faster, but you risk freezing the evaporator. Now, watch the system pressures rise as the water evaporates and the heat in the system and stabilizes and equalizes. This can take a long time if you have a mechanical radiator fan. The point where the pressures remain relatively constant is called equalization.

Here is the key:
(After wetting the condenser) As you are watching the high side pressure rise from 160psi through (potentially) about 205psi the LOW side should REMAIN from 21-24 psi. If the high side never sees 145+psi you are still low on charge as long as the ambient is 85 degs or above. If as the high side needle swings through 160psi the low side is still below 20psi, you will add more refrigerant AFTER wetting the condenser again and dropping the pressures. Keep doing this until the low side remains at 21-24 psi while the high side swings through 160psi and finally settles at equalization (no more rise) Keep the engine rpms constant and wait for equalization (or close) each time before wetting and charging. If you are going carefully and slowly you could see a high side over 225 at equalization BEFORE you reach a full charge. The high side will DROP as you come closer to a full charge. Be aware that if you over-charge, the high side will climb again and never come down.

Note: If the ambient air is above 95 degs, stop watching the low side after the high side climbs past 205 or so. Especially if you have weak fans.

Note: Take your time and wait for equalization and water evaporation off the condenser before adding refrigerant. An overcharge can occur with no more than an extra 1.5 ounces of refrigerant!!

You can double-check your work at any time (and I suggest doing so) by waiting for full equalization and stabilization of pressures. Then, carefully MIST water into the condenser SLOWLY SLOWLY dropping the system pressures and watching for the same readings on the gauges as listed above.

When finished you should have a sweaty return line all the way back to the compressor. When the return line begins to feel chilled over the first portion of its length, you are approaching full charge. Do not forget to reconnect the low pressure cut out switch!

Do not consider your vent temps accurate until the vehicle has been driven for about 10 minutes at moderate highway speeds!!!! Idle low side pressure should not exceed 40 psi (34-38 actual) if everything is working well; good fans etc….

The idea here is that the compressor should NOT cycle when ambient air temps are above 81-84 degs.

Interesting note for tech heads: If you are charging SLOWLY. You will find at first that the high side will be at a higher pressure, after equalization, on a low charge than at a correct charge! Remember, raised heat = expansion and/or pressure.
Why: (basically)
Within a certain range, the pressure in the condenser (high side) is MUCH more affected/determined by the temperature of the refrigerant than its volume.
ALL THINGS BEING EQUAL, the condenser has the ability to lower the temperature of the refrigerant passing through it “X” amount and no more. The compressor, in compressing the refrigerant, heats or raises the temperature of the refrigerant “Y” amount. Lets say the temperature of the refrigerant entering the compressor via the return line is “Z”. So the final temperature “T” of the refrigerant that gets to the orifice/exp valve is: Z+Y-X=T
If we could lower the value of “T” the entire system would work more thermally efficiently and at lower pressures on the high side. So, ALL THINGS BEING EQUAL, you could 1. get a larger condenser and raise your “X” value or 2. lower the value “Z”.
A full charge on an A/C system will not only have enough refrigerant in it to keep the evaporator “chilled”, but JUST ENOUGH that the line leaving the evaporator and returning to the compressor will also have substantially cooled refrigerant in it THUS LOWERING YOUR “Z” value!! Hello!!
Note: Over charging will allow actual condensed refrigerant (liquid) to make it all the way back to the compressor. As we all know, you cannot compress a liquid…boom/screech.
----------------

Re: Suburban A/C fix + Vintage Air?
 

It kills me a little that Hatzie sent that message while I was charging the beast and did not see it until after!

Boys and girls, here's the report.

65 degrees ambient air temp.
3:45pm
Front Vent temp: 82
Rear: 80
added one can of refrigerant (12oz). At some point during this HOUR I actually read the directions and shook the can, did the 12 to 3 tilt. This speeds things up.

The fans kicked on when they should, the compressor kicked on, everything was looking good. No blown fuses or craziness.

So far so good.

https://photos.smugmug.com/VehiclesO...IMG_9731-M.jpg

4:32pm
Front Vent temp: 88
Rear: 81 (we closed the windows!)

Added second can. 11.9 oz

4:50pm
Front Vent temp: 64
Rear: 68

Can no. 3 12.05 oz

5:38pm
Front Vent temp: 50
Rear: 52

Now we are cooking with gas!

As a test I put the thermometer in my CAR: 44 degrees coming out of the dash. This was now what I was shooting for.

At this point I slowed down (It was already slow) and measured 1-2 oz at a time, waited 5-10 minutes and compared the vent temps.

As soon as the temp started to stabilize (could not get it to drop further) I stopped.
Temp from the dash was 48 degrees in the front and 49 rear.

Should I be happy with those numbers?

Figure out the way to measure these that makes sens for you!

https://photos.smugmug.com/VehiclesO...IMG_9734-M.jpg

Honey, Have you seen the kitchen scale?

https://photos.smugmug.com/VehiclesO...IMG_9736-M.jpg

This was the lowest temp I got out of the front.

https://photos.smugmug.com/VehiclesO...IMG_9749-M.jpg

Re: Suburban A/C fix + Vintage Air?
 

I am not a professional but I would be happy with that, especially for not pumping down the highway.

Re: Suburban A/C fix + Vintage Air?
 

Also here were some pressure readings while running things at the end.

https://photos.smugmug.com/VehiclesO...IMG_9739-M.jpg

Re: Suburban A/C fix + Vintage Air?
 

Finally got out to drive the Burban:

Just around the block, looking much better!:
https://photos.smugmug.com/VehiclesO...IMG_9780-M.jpg

Then to the parts store and a brief stint on the highway:

https://photos.smugmug.com/VehiclesO...IMG_9788-M.jpg

PARTY PEOPLE we have some REFRIGERATION! 36.5 Degrees indicated!
I'm frankly shocked and amazed!

https://photos.smugmug.com/VehiclesO...IMG_9781-M.jpg

Re: Suburban A/C fix + Vintage Air?
 

Wow.....

Re: Suburban A/C fix + Vintage Air?
 

I hope this thread encourages someone to go for it! A big thanks to everyone who pitched in and gave advice, or even just watched on this thread, it helped keep things rolling!

Meanwhile here is a quick summary of what it took to get cold air blowing out of the vents:

First let me say I'm a hobby mechanic. The idea of adding AC to my rig was pretty ambitious if not crazy sounding, considering I knew NOTHING about how AC actually works. I only know a *little more now, but I get how it all goes together now.

The real scary part was there are very few "real mechanics" that would tackle a job like this, so if I gave up along the way there was no "higher authority" I could petition to finish it.

My theory is this: once you 'own' a vehicle of a certain age, you OWN the problems. Very few "professional mechanics" are REAL problem solvers. There is just no money in it. This makes me VERY grateful to this community, for the moral support and technical advice here.

I committed to this project two years ago, and made some pretty good mistakes, which stalled me out considerably. I bought the wrong sized compressor (and bracket) which was not a trivial expense.

Calling "Classic Auto Air" and talking to Mike Oliveras was the best thing I did on this project and he set me straight and helped me size the system and get the parts I needed. In the end I complete this job

Here is a rough cost breakdown:
Salvage Yard
Rear AC Unit, dash switch (and hoses I ended up not using): $150
(I bought some other things so I think this is close)

Classic Auto Air
Compressor
Bracket
D-rings to mount hose
High side, low side hose (35ft?)
Parallel flow condenser
Mounting brackets
All AC line fittings
$1,400

Things we forgot
Trinary switch (summit racing): ~$50

Miscellaneous
Wiring, relays, connectors, crimpers, etc
Refrigerant

Tools
Gauge set & Vacuum pump: $140
ACCrimper: $140
Orifice tool: $15
refrigerant tap: $15
Thermometers: $20

Doing the job yourself and having it work: Priceless

Things I would do differently
Spend time exploring hard line options.
I doing research it seems there are ways to make your own "braze on" hard line AC connectors. Also vintage air has a product called "u-bend-em" which is a hard line connector that seems like it would be great to get through the firewall.

Do more research on charging the system for maximum cold. (turns out after my test run I was ok!)

Other Options
Classic Auto Air and Vintage Air both make "kits" where you can remove all the stock stuff and replace it with all brand new parts (front AC only) for something like $1500. Plug and play, and this is probably a great option.
I don't think anyone makes a dual system kit, so you would still face some of the same challenges: What size compressor, how to run lines to the rear, and what rear unit will fit and not look terrible (why I went with stock).

So of course the expense rarely makes sense considering you can buy a suburban for the cost of my AC System!

...THERE ARE MANY LIKE IT, BUT THIS ONE IS MINE.

Re: Suburban A/C fix + Vintage Air?
 

Solid, logical feedback.

I went through the a/c when building my Dually. I did the parallel flow condenser to help w/the 134 refrigerant. New hoses. Then relied on local shop/dealership guys to get it leak tested & correctly charged. I've never got it to work correctly.

It would blow cold (well, cool) sitting @ idle. As soon as you start driving? It shuts off. My guess is head pressure but I couldn't get anyone w/the equipment to keep @ it like what you went through. Congrats on a job well done.

Re: Suburban A/C fix + Vintage Air?
 

I have cold a/c on my crewcab, but I put a 10" fan on the front of the condenser so it stays cold while sitting in traffic. gotta keep air moving across the front.

Re: Suburban A/C fix + Vintage Air?
 

Mine has a functional OE pusher as well. I feel the issue is the volume of oil + refrigerant within the system but seem to not get buy-off from those that charge the system.

Re: Suburban A/C fix + Vintage Air?
 

You can rent the gauges for free from O'reillys, and find out what pressure you have..

https://www.oreillyauto.com/detail/b...+gauges&pos=19

Re: Suburban A/C fix + Vintage Air?
 

They'll never tell you that.
That would be admitting they screwed up and didn't clean the old oil out of the system thereby ovrefilling with oil.

Re: Suburban A/C fix + Vintage Air?
 

My plan is to have it flushed & refilled. We shall see. It wasn't a big deal @ the time because I don't drive it that often. But, I want it working as a selling point if I decide to test the waters @ some point.

Re: Suburban A/C fix + Vintage Air?
 

Congratulations! There may be others but I bet they are not 36 degrees inside! May you enjoy this AC for a long time sir!

Re: Suburban A/C fix + Vintage Air?
 

x2!

Re: Suburban A/C fix + Vintage Air?
 

Awsome, well done I've been waiting for the results.:metal:

Re: Suburban A/C fix + Vintage Air?
 

Tomorrow I take this beast on a 9 hour road trip to do some *Wheelin' in the desert. Supposed to be mid to high 90s the whole week.
THAT is going to be a good test!

I've only taken it on a couple of short road tests, but so far so good. Wish me luck, I'll check back in, in about a week!

Re: Suburban A/C fix + Vintage Air?
 

Good luck! May the cool be with you!

Re: Suburban A/C fix + Vintage Air?
 

That'll be a perfect test, awesome job! You've inspired me to tackle A/C fixing on my '85 Suburban.

Re: Suburban A/C fix + Vintage Air?
 

thats awesome you got it working. Hope it stays that way your whole trip.