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  #1  
Old 04-15-2011, 11:08 AM
vstech's Avatar
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OK.
the A/C systems in our cars have plenty of obstacles to removing heat from our cabins.
Clean bend free fins and tubes should be the first thing any of us do to our car's a/c condenser, AND evaporator.
next it the fan clutch, and aux fan operation.

pressures in these charts are what we want to see with a proper operating system


This thread is going to be full of answers for our various automobile systems!






adding fans may help a little, but the problem with the older 123's lies in the huge series coil up front. it does not flow like 134 needs, thus lower volume of charge is required to keep the system operating... that low volume cannot handle the heat of the cabin without serious pressure spikes, and pressure is heat, it's a mad cycle.
IF you can find a condenser from an 85 123 it'll help a lot. but you'll still be pumping with an R4 compressor... are your windows tinted? light color paint on the car?

Quote:
Originally Posted by Manual Life View Post
There are no leaks. The system held a vacuum for 4 months and has been good for a couple weeks. The recharge wasn't yesterday.

Oil added, none was in it. The vacuum could not reach 0 without the oil. I assumed I had a leak but that wasn't the issue. After adding the oil the vacuum reached 0. I don't know how or why. It was recommended by an old mechanic.

I can exchange the 134 but wasn't sure I could locate some 12. I assumed it was difficult to come by. I can unload the 134 at a friends shop at no cost, as is didn't cost me to charge it, but where would I locate some r-12?
a system with some pretty big holes can hold vacuum for months and leak out pressure in a few minutes.
to test a refrigeration system with an operating pressure of excess of 200 psi with less than 15 psi of atmospheric pressure is crazy and a really bad idea.
if it held, it proved nothing, if it leaked it destroyed the dryer and added moisture to the system... neither solution is helpful in testing a refrigeration system...

This thread is going to be strictly edited, and will include only approved A/C practices.
quality hints and tips as well as rules to follow!

Links to DIY and other Climate control articles

Quote:
84 300D

After a year and a half I finally got around to charging my A/C. It's so nice to have it and enjoy the quiet of windows up.

And, I assume if I doubled up on the fans for the condenser I would have cool air full time. As it is it warms up a little at idle and I am thinking this is the result of switching from R-12 to 134.

If that's not the problem let me know and what I can do. If it is the problem has anyone doubled up on fans? If so which fans?

Otherwise it works very well. I am happy to see how cold it is. I heard rumors that even a good a/c system didn't get very cold on these old cars.
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Last edited by vstech; 06-06-2011 at 07:04 PM. Reason: organization
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  #2  
Old 04-15-2011, 01:06 PM
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Quote:
Originally Posted by billhard View Post
If you are sure your system isn't leaking why not go back to R12? After I rebuilt the system on my 85 I charged with R134 and ran it for about 2 weeks until I was sure it wasn't leaking. Then I took it to a local AC guy who evacuated the r134 (even gave me credit for it) then charged me with R12. This wasn't cheap but it works really well.
For the record ...
Do you want to describe what you did with regards to the oil in the system ?
In other words... did you have to plan ahead and make decisions about oil based on what you planned to do in the future ?

The more usual way to check for leaks is to pressurize with Nitrogen and four ounces of R22 ( which the EPA allows you to vent legally )..
This would negate any potential oil compatibility issues .
And would usually cost less than having the R134a evacuated by a pro with the proper equipment charging for their time...
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  #3  
Old 04-16-2011, 12:11 AM
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Some oils are specified for R134a and some for R12 and I think some will do for both.. but I do not know how well they will do for both in our NON SUMP Delco R4 compressors.. thus I have not investigated it..

Many auto parts stores.. if you get the $20 over the internet EPA license based on an OPEN BOOK TEST... will sell you R-12... you have to ask them for it...and many of the idiots at the front counter see a request so seldom they do not even know the store has it... but often getting it off Ebay is cheaper..

Last edited by vstech; 06-06-2011 at 07:00 PM.
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  #4  
Old 04-16-2011, 12:23 AM
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I'll start the ball rolling.

to properly test a refrigeration (A/C) system for leaks you need PRESSURE! it must be in the form of a gas. NO liquid can be present or it invalidates the test.
Standard test gas is Dry nitrogen. CO2 can be used as can any gaseous refrigerant, but refrigerants are NOT legal to vent, so it's not a good idea to use them unless you have recycling equipment.

testing for leaks with vacuum is a ridiculous plan. I know MANY shops and individuals think it's a good way to test for leaks. It is NOT!
on a rigid piped system (home a/c or refrigerators etc) vacuum can and is used to test for leaks as well as moisture presence... but a DIGITAL micron gauge is required for the test.
mobile refrigeration with flex lines, and semi hermetic compressors with a shaft driven compressor simply cannot reliably be tested with vacuum. the rubber will mask a vacuum leak test, and the crank seals will vent moisture into the compressor, and the dryer in short order...
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!
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  #5  
Old 04-16-2011, 12:33 AM
vstech's Avatar
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Quote:
What are the best sources for dry nitrogen/R22?
craigslist.

Quote:
any HVAC supplier will sell you a tank for 200ish, and a regulator for 50 ish... craigslist sells tanks with regulators for 50ish..
you can also use CO2 which comes in a smaller lighter tank with a MUCH larger useage at lowes or home depot for 90ish. you would then have to rig an air chuck adapter to hook up your manifold to.
you can also use one of those helium baloon tanks, but one 30.00 tank will just about be empty after one use.

Quote:
Originally Posted by zeke View Post
What are the best sources for dry nitrogen/R22?
Your local Welding supply shop.
Ebay for R22 in 15 oz can...
which I am still trying to figure a way to split three ways evenly... I guess an accurate scale would be good too.. just like you would do the refrigerant if you used a big tank to install it...
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Last edited by vstech; 06-06-2011 at 07:12 PM.
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  #6  
Old 04-16-2011, 12:42 AM
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Good start..
Except R22 in the amount of FOUR Ounces... put into an automotive system with nitrogen to pressurize it.. IS LEGAL.... per EPA... so that people can test under pressure..as you recommend...
the reason pressure is needed is so that the orings involved are in their WORKING position..
not being pulled IN by vacuum... when they need to hole being pushed out by pressure...
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  #7  
Old 04-16-2011, 01:01 AM
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So what tools are necessary to pressurize the system with something such as nitrogen or co2? I have always done the vac-down method, but that's because I was none the wiser...
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  #8  
Old 04-16-2011, 01:08 AM
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You were doing the correct thing ... that is for getting the moisture out...so that acid does not form from the mixing of moisture and the oil in the system... causing flakes to come off the inside and plug up tiny holes ..like in the TXValve.
We are just saying that THEN... to test for leaks... you need pressure..
you can use a normal set of hoses and gauges... there are regulators which fit on the nitrogen tanks just like Oxy or Acet...
then that hooks to your AC gauges and you open the proper valves...
I have a nitrogen tank and gauges...will post pics... but can not find my dang camera... been missing for four days...
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  #9  
Old 04-16-2011, 10:25 AM
vstech's Avatar
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Quote:
Originally Posted by francotirador View Post
Hello: I have a 1990 300SE and I would like to revert the system to R12. It was converted to R134 by the original owner. I read a long thread posted hereon where the original question was essentialy "how do you convert back to R12 from R134?" That question was posed a few times during the thread and it was really not answered.

So, please tell me, how do you convert a system from R134 to R12? The compressor I have is good for both types of refrigerant. I understand a different oil must be used. I know the drier has to be changed and the correct amount of R12 must be introduced into the closed system. I imagine the Schrader valve fittings must also be changed.

However, what I don't know is if there any other fittings, seals, hoses...that must be changed for use with R12?

If you would post the details of the R134 to R12 conversion I, and many others, would greatly appreciate it.

Thank you.

Great question.
several levels of answers can be dependent on what the 134 "conversion" entailed.
first, the Oil in the system. if you do not know what kind was used, it's best to replace the compressor, the expansion valve, and the compressor manifold, with the dryer and flush the remaining coils with oil/refrigerant flush, then add the correct amount of mineral oil to the system, pulling a hard vacuum, then weighing in the correct volume of R12.
this is the BEST method to convert back to 12.
PAG oil is not compatible with R12, Ester is. if you don't know, it's best to assume PAG was used, and do it right. however, since doing it wrong will destroy your compressor, requiring you do do all that stuff, if the wrong oil is used, and will not if Ester is in there, simply evacuating the refrigerant, measuring how much oil came out with it, and replacing that with the same amount of ester oil, then flowing the weighed amount of R12 will put the system back to R12. however you will still have the 134 fittings on the system... if you try to remove them, you can damage the lines (don't ask how I know this) this is why it's needed to replace the compressor manifold.
then lastly the 134 sticker needs to be removed.
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Last edited by vstech; 06-06-2011 at 07:06 PM.
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  #10  
Old 04-16-2011, 11:16 AM
Yak Yak is offline
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Removing R-12-to-134a-adapter fittings is primarily dependent on the original conversion. Since these kits are sold in any autoshop they may/may not have been "properly".

Some may have been spot-brazed in place, others are simply screwed on. Some kits appear to have thread-locker on the new fittings while others don't. Some conversions only changed the low-pressure/blue/"fill-port" on the top-front of the engine to a 134a fitting and left the original R-12 high-pressure/red/"service-port" alone.

Modifications to fittings may affect the integrity of the schrader valve directly beneath it. The valves should have caps with O-rings in them.

Before attempting any conversion/de-conversion you really need to inspect the whole system and be prepared to invest in new components where necessary. This includes the proper operation of the heater and the cooling system of the car.

Some new components (e.g. R-4 compressors) may not honor the warranty if used in an R-12 "de-conversion". You need to decide if the warranty vs. performance trade-off is worth it when selecting what refrigerant you use.

The A/C lines and fittings, even though they're on an otherwise metric car, are SAE sized. Having the right tools is also very important.

You really cannot assume anything when you're working on the A/C.
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Old 04-16-2011, 11:32 AM
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"Having the right tools is also very important."--Yak
When dealing with AC lines.... it is always suggested that two wrenches be used.. and often the proper wrenches will be what is called ' Line wrenches " or "?"... these are open end wrenches which wrap more than 180 degrees around the nut. But are still large enough on the open side to fit over the tube next to the nut or fitting... so they can be used in tight places to protect the line from being crunched...which is the most important place to exercise caution because having to replace the line in a tight place is really a chore.
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  #13  
Old 04-16-2011, 01:35 PM
vstech's Avatar
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Quote:
Originally Posted by Manual Life View Post
This thread exploded. In the case that you already did not know, I know virtually nothing about a/c systems. And, I had a tech from Aamco do the work. We did it at his house because he had everything required.

He added 2 oz. of a/c oil after the system was evacuated. Following the oil he added the 134.

When I say "0" I mean on the evacuation. Without oil the there was not a full evacuation.

As is, I'll go ahead and test the system with dye and go from there. In the meantime search for R-12
OK.
let's start over.
the oil was added to a functional system, or was the system cleaned out first?
zero on a refrigeration manifold gauge is open to the atmosphere. or simply pressure removed.
a properly evacuated a/c system will read pegged to 29" on the lower scale of the compound gauge. not zero.
and that is NOT the limit of the scale, at 28.9 inches of mercury, vacuum there are microns of scale between it and 29.2" perfect vacuum. I like to shoot for stable 1000 microns in automotive evacuation that will hold.
it's REALLY hard to go lower than 1000 in a semiherm system. it's nearly impossible in a leaking system to get it below 2000 microns. and it will not stay there long. oil can slow the movement of atmosphere into the system through the pores in the lines, and the spaces between the seals. but just adding oil to the system will not move it around enough to do it. it's gotta be fed through an operating system to spread.

Unless you are discussing scientific gauges...
then: One Atmosphere = 14.7 PSIA = 0.0 PSIG

Perfect Vacuum = 0.0 PSIA = - 14.7 PSIG
__________________
John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

Last edited by vstech; 04-18-2011 at 01:37 AM. Reason: corrections, thanks to MattL etc...
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  #14  
Old 04-16-2011, 01:45 PM
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29.9 is not perfect....
the barometric pressure varies....and 2 niner niner 2 is the reading on a ' standard ' day... at sea level at a specified temperature...
So perfect on any given day has lots of variables to factor in... but most techs have a reading on their machine which they quit once reached...
Vstech is referring to the fact that our AC's have a controlled leak at the compressor.. for lubricating the compressor front bearing.. making this NOT a Hermetically sealed system the way a refrigerator or your home AC system is... the compressor sitting in oil and all the lines soldered or the like...
I do not know if Manual Life has these answers to give us.... or even if he can get them from his friend... it is a good chance to go over some of the basics though...important basics...
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  #15  
Old 04-16-2011, 02:21 PM
Yak Yak is offline
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Quote:
Originally Posted by Manual Life View Post
84 300D

After a year and a half I finally got around to charging my A/C. It's so nice to have it and enjoy the quiet of windows up.

And, I assume if I doubled up on the fans for the condenser I would have cool air full time. As it is it warms up a little at idle and I am thinking this is the result of switching from R-12 to 134.

If that's not the problem let me know and what I can do. If it is the problem has anyone doubled up on fans? If so which fans?

Otherwise it works very well. I am happy to see how cold it is. I heard rumors that even a good a/c system didn't get very cold on these old cars.
I'm assuming this is still the original question.

It sounds like your system is operating normally with/without R-12 and you're considering options to make it better.

Yes, going back to R-12 would help. But as you've possibly already experienced it's not straightforward to source R-12. You can buy it on e-bay, craigslist, etc, but caveat emptor. If may say R-12 but be some variation with 12 in its name. You may be able to buy real authentic R-12 in some autoparts stores locally but you're supposed to have the EPA certificate. Purportedly easy to get online for minimum cost. You'd need to flush the system to get incompatible oils out, then re-charge after proper leak testing (vacuum as a rough test, then pressure as a final check - my system held vacuum, but leaked under pressure so I'll vote for a pressure test prior to installing hard-to-source R-12). I tried 3 shops in San Antonio (including Carlisle) and none of them wanted to put R-12 into my car.

Adding smaller diameter fans to a 134 conversion might help if it increased the volume of air across the condensor. This is probably a last ditch band-aid attempt.

Cleaning the existing evaporator of dust/crud might help since you'll get better airflow across the cool surface. There are posts on how to do this.

Modifying the vent flaps to do "re-circ only" might help since you're cooling previously cooled air.

Making sure the radiator and condensor fins are clean/clear might help (a swarm of monarchs or snouts in Texas will clog that pretty quick).

Since A/C feel is sort of subjective, I'd recommend putting a thermometer in your driver's side vent and finding out what the output temps are (low cost, no-tech meat-thermometer style available at Autozone or elsewhere is fine). Nothing appeases the opinionated A/C crowd like numbers and data. That way you'll have a reference of how good your current cooling is and what temps you might expect.
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