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R12 to R134A questions on a 90 sub.

y5mgisi

y5mgisi

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I got a split in one of my a/c lines a while ago, and i lost all the refrigerent out of the system.I replaced the line, but I've heard that i cant just go get a refill of the R12 and that i have to convert to the R134a stuff. I have also herd that to do this i need to actually convert somthing over and that it is not just as simple as puting the new stuff in. Can anyone tell me what all needs to be done? My buddy has the vacume pump and the manifold with all the guages and stuff so thats not a problem. And hes not exactly blind on the subject like me we just dont know exactly what all needs to be done in order to have a fully(properly) functioning R134a system in my truck. /forums/images/graemlins/1zhelp.gif
 
The problem is that when air is introduced into your system it brings moisture in also. That contaminates the accumulator dryer and it will never work right no matter how long you pull a vacuum on it.

You could recharge with R12 if you replace the accumulator dryer. But it would be a good time to go with R134a in my opinion.

We just converted my sons dual AC system to R134, we had to have several hoses reworked etc.

If I were you...I would go ahead and remove the accumulator/dryer, and the orfice tube, disconnect all the fittings (replace the orings with the newer green ones for R134a when reassembling), flush each line seperatly, do the rear lines also.

I wouldn't try to flush through the rear evaporator.

Flush the front evaporator and condensor.

Remove your manifold/lines from the compressor, flush them.

Remove the compressor and rotating the pulley, dump all the oil out (assuming it has some in it:-)).

If you suspect the compressor (as in it's performance or if it might leak) at all, take it down to the local AC shop/supplier and have them test it ( will ensure it works and doesn't leak).

While you are there get

a new accumulator/dryer and an orfice tube,
it's also probably the cheapest place to get the flushing agent and the R134a and an assorted box of O-rings,
and ester oil (for R134a) also.

Anyway after you flush every thing until it is reasonable clean,

reassembly everything - putting most of the ester oil into the compressor and dividing the rest up into the lines and condensor, oil the orings too.

Oh - don't forget to get the conversion fittings at the AC supply place.

Pull a vacuum for 1 hour. Let it sit for 15-30 minutes, it shouldn't fall much if any.

If the vacuum check is good, jumper your low pressure cutoff switch and start dumping the R134a in.

Be aware the dual system uses an orfice valve in the rear evaporator and until you get half of the R134a in or so it has been my experience that the rear evap bypasses the R134a from the front (makes you think you installed the front orfice tube incorrectly or forgot it /forums/images/graemlins/smile.gif). The result is the rear is blowing cold air for a while before the front cools down at all - until you get the charge mostly full.

My sons 77 Sub dual air works really well on R134a. You should need about 85% as much R134a as R12 and your pressures will be about 15-20% higher.
 
WOW! lots of real good info. Pretty much answered all my questions. Now how do i go about "flushing" the lines? Do you think the r134 blows as cold or colder than the r12? What are the benifits of r134? is r12 way more expencsive? And when im puting in the new 134 stuff shuold i have the engine runing? and where/what is the lowpressure cut off switch. so what should i expect to pay for everything by the tme its all said and done? Sorry for all the questions i just realy want to do this right the first time.
 
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WOW! lots of real good info. Pretty much answered all my questions. Now how do i go about "flushing" the lines?

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I have used 2 or 3 different products. The one I like the best is pretty much just a solvent that is compatible with the ester oil. I can get the name brand off the can at home tonight. Other kinds I have got from checkers/auto zones have had some oil in them - way less effective in my opinion. ( you won't believe the crap that comes out of the condensor - especially if you have had a compressor fail before). The least expensive way is do attach hoses to the into and outof, put the outof hoes into a empty plastic gal water/milk jug, pour a few ounces of flush into the component or line and blow through it with your air compressor, then look into the bottle ( turn off the air first /forums/images/graemlins/shocked.gif and evaluate the flush contents. Use safety glasses. Do that until the stuff coming out of the component is free from bits of metal/gunk and is mostly clear. On really dirty components you may not ever get it clear. On some things it will be clear though. Never flush your compressor or accumulator. Always replace the accumulator, and if the orfice valve is dirty replace it too. They are too cheap not to IMO. Some people just clean them off.



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Do you think the r134 blows as cold or colder than the r12??

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Yes, yes, yes, yes

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What are the benifits of r134? is r12 way more expencsive??

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R134a can be bought for about $6 a can (8 or 12 OZ?), it can be bought without a license. R12 is 10 times that amount and still climbing. You need a license to buy it - it is pretty easy to get though (the license).

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And when im puting in the new 134 stuff shuold i have the engine runing?

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The engine running with the AC on max cool and full blower (front and rear). I assume your buddy knows the basics about charging refrigerant i.e never open the high side valve when charging, etc.. He should if he owns the equipment. Its the same for r134a as R12.

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and where/what is the lowpressure cut off switch.

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It is the 2 prong round rubber connector on the side of the accumulator / dryer. It will need to be removed and reinstalled onto the new accumulator/dryer.


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so what should i expect to pay for everything by the time its all said and done?

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If you go to an AC supply house (like AAAPAK on the web - local to me):

New compressor if you need one - A6 - $130-140
Accumulator/dryer - $40
Orfice tube - $6
Box of o-rings $12 - way more than you will need (otherwise $.75-1.00 a piece)
Gallon of flush - $10-15
a bottle of ester oil $6-10
Rebuilding an AC line is about 2 bucks a foot for the rubber, $1-2 bucks per swage, $1-2 per weld, and a few more bucks if you need a special 90 degree or something, so say $120 for a complicated or long line or $30-50 for a simple line.
Conversions fittings $4-6 apiece - need 1 hi, 1 lo.

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Sorry for all the questions i just realy want to do this right the first time.

[/ QUOTE ] That is the only way to do it. I had to do quite a bit of research and reading to get comfortable doing it. The after you do it a couple of times it all seems pretty simple.

As far as the R134a leaking through rubber lines meant for R12, that was a common theory when these conversions were first started. But in reality a R12 line that has been in use has a barrier of oil molecules, plus other residue that form a pretty good barrier to R134a. New lines need to be the R134a type.

I forgot to tell you in the first post...get a spray bottle of soapy water and look for bubbles at all connections during and after charging. Sometimes a joint or connection can be good under vacuum but under pressure it will leak. Especially check you conversion fittings after you have completed the charge and removed the rig hoses. Sometimes they leak until the cap is put on. Put the cap on and check it again. Oh....and make sure you remove the schrader valves from the old R12 fittings if that is the kind or conversion fittings you get. Some you need to some you don't. Always check the fit - ie examine them closely before you install them, some guys that sell them don't really know. You can tell by looking at how long the schrader valve is in the conversion fitting.

Take you time, it's great to be able to enjoy cold AC for pennies on the dollar compared to what a shop would charge you.
 
Ok sounds like we will be able to ge it done. ANd thanks ALOT for all your help. Very valuable information to say the least. Just so you know what im dealing with exactly its on my sub. As far as i know nothing has ever been changed before. The line that cracked is a hard line up by the canester thing(acumulater?) I think i must have steped on it or somthing while working on the truck. It isnt a big crack at all, infact it was only letting the stuff just bubble out slowly asif it only had a pinhole fracture. Im thinking i can clean that part real good and JB weld it and it should be good. I dont think i should need any lines redone. And i havent ran the compressor or turned the a/c on at all sence i noticed the crack in the line bubling. so the compressor should be good. Once again thanks again and again for all your info and advice. If anything else comes up that you think i should know please let me know. /forums/images/graemlins/waytogo.gif /forums/images/graemlins/peace.gif
 
R-12 is no longer being made.It was banned because it is a clorinated type of refrigerant that causes ozone depletion. R-12 is by far a better refrigerant that R-134 A. You loose system Capacity with 134A. The reason you have to flush the system is that the lube oil that was used with 12 is a mineral based oil. the new oil that you have to use with 134a is called Polyal ester oil, It is a solvent based oil. if you just add this oil with your old system it will attack the o rings. you don't have to change the hoses just the o-rings. there are several brands of r-12 replacments available that I would consider using that are drop in replacments instead of the 134a.......you do not have to change anything /forums/images/graemlins/thumb.gif /forums/images/graemlins/thumb.gif
 
It doesn't need to be that complicated or expensive. First replace the bad line. JB weld will never work if it is on the high press. side. Normal pressures will be 250-300 psi. To convert all you realy HAVE to do is get some 134 conversion fittings, pull a vac. for 30 min, charge (add) the system w/ 6-8 oz of PAG oil (compatable w/ r-12 and 134a) and charge with 75-80 percent of the factory recaommended charge. Easy. Ihave been doing this for years, 3 or 4 a day in the summer. Pulling the 30 min vac will remove the r-12 oil and boil out the moisture in the system. The only time you really need to change the accumulator is when the system has been left open for a long time or if the system is contaminated w/ metal from a compressor failure. I also extensively researched this subject when i worked for the dealer and came up w/ similar info to azblazor. Very good info IN THEORY but also unnecessary. I have a very high sucsess rate w/ this method. BTW I charge less than $150 at my shop including fittings, oil, 134 and labor and make a killing. (i can by 30 lb cans of 134 for less than 55.00)
 
Good points, I was not as clear as I should have been. I would only replace the accumulator if the system had been opened to atmosphere for a fair amount of time. The orfice tube I would inspect for debri if the system was opened.

I have done several vehicles just exactly as you have described. As long as the system was working before on R12 it should work fine when converted as you described. Which is pretty much what the converion kits are.

But on a system that had a failed compressor or that had been non functional for a long time I would go the extra mile with flushing, orings, accumulator and orfice tube.
 
I disagree. You'll never get the old oil out of the accumulator without replacing it. It should be replaced.

The difference between doing this job correctly and doing it until the system works are pretty clear in my opinion.

Hack way:

Charge with new refrigerant and oil. Install new fittings and put on the sticker.

Professional way:

Replace all black o rings with green or blue ones. Replace accumulator. Flush system. Pull into vacuum. Add oil and refrigerant with new fittings and sticker.

Your way works great for a customer that doesn't want to spend $$ and may only keep the car for a few years. Those of us enthusiasts really need to go the extra mile--but it's worth it in my opinion.
 
The sticker!!!! I knew I was forgetting something /forums/images/graemlins/smile.gif

Actually the PAG oil has worked pretty well for me if the system was OK to begin with.
 
I don't think there is really any question as to whether it works or not. Of course it does, otherwise people wouldn't be doing it that way.

In my opinion though there is a difference between making it work and making a professional repair, and doing things like changing o rings, flushing the system, and replacing the accumulator are things that a professional seriously considers while your average hack just throws it together.
 
OK, again lots and lots of usefull information. So if i use the PAG oil, Will i still need to change the O-rings? And where are ALL the o rings that i should change? How many? Another thing im confused about is procedure. I guess in a round about way i was looking for a write up. Like step by step style. I'd imagine my buddy has the answer to some of these questions but i cant get ahold of him. Do i put the oil in the shrader valves? Can i get all this stuff like at an autozone or should i try to find a shop that specializes in this type of stuff? what about the acumulator? Do i just go up to the parts desk and ask for an A/C acumulator for a 90 chev suburban? How do i know what the manufactures recomended amount of refrigerent was so i know how much 134 to put in.? THanks again You all have been more than helpfull! y'all are s /forums/images/graemlins/thumb.gif /forums/images/graemlins/ears.gif
 
If you pull a vaccum on the system long enough you will get 95% of the oil out of the system. Use a PROFESSIONAL a/c machine and you can actually measure the amount of oil removed. The oil and refrigerant charge amounts are right on the accumulator usually.

I disagree about this being the hack method. POssibly the extensive way could be considered the anal method. Assuming an otherwise functioning system that has had a leak repaired there is no advantage to replacing a bunch of good parts. Sounds like a parts guy diagnosis. It is very easy to fix something if you simply replace everything. Much more difficult to acurately diag and only replace what is necessary.
 
10-4, azblazor. Also on a system that has had a compressor failure a pancake (inline) filter should be installed. you would never believe all the metal that gets in there. Either that or you could just change ALL THE PARTS and be sure. /forums/images/graemlins/smirk.gif
 
Well how would i go about geting a drop in R12 replacement? How much does that cost. On thing that hasnt got answered yet was if i use the PAG oil will i need to change the o-rings?
 
The o-rings will be fine. I just installed a new evaporator on a Buick that was originally r-134 and the new evap had black o-rings.
 
What do You guys mean by pulling a vacuum on it?? My pump siezed up, so Im gonna get a new pump (well outta u-pull it) do I also need a new accumulator (?) and is that the big canistor on the passenger side firewall?? I bought some R134 conversion kit...comes with 3 cans of refrigerant/oil, and some new fittings, no new O-rings tho, will I need to get those, or is this one of those "hack job" kits? it does have the sticker /forums/images/graemlins/rotfl.gif anyways I need some help on this too, and I dont know JACK about AC systems, so explain everthing by what it looks like, I have NO IDEA what the real names for the stuff is.
 
So i dont need to do o-rings? but i do need acumulator? The system has only had a leak for about a month so i dought its all rusted up or anything like that.
 
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What do You guys mean by pulling a vacuum on it?? My pump siezed up, so Im gonna get a new pump (well outta u-pull it) do I also need a new accumulator (?) and is that the big canistor on the passenger side firewall?? I bought some R134 conversion kit...comes with 3 cans of refrigerant/oil, and some new fittings, no new O-rings tho, will I need to get those, or is this one of those "hack job" kits? it does have the sticker /forums/images/graemlins/rotfl.gif anyways I need some help on this too, and I dont know JACK about AC systems, so explain everthing by what it looks like, I have NO IDEA what the real names for the stuff is.

[/ QUOTE ]The purpose of pulling a vacuum on this system is to remove moisture. what happens is under a vacuum you lower the boiling point of the water that is in your system. once in a vapor state it is pulled out by the pump. as far as the drop in replacments for R-12 you do not have to change the O" rings if you can use regular refrigeration oil ( mineral based)with that perticular replacment...
 
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