R1234

Hello,
I have finally assembled and installed all the parts to my 68 a/c system. The system is tight and holding 24 inches of vacuum for about 24 hours now. My home made vacuum pump will only pull down to this amount.
I'm going to try the 134a. One question that I have is: Can I hook up the 134a can to a set of r-12 charging hoses like the ones you can buy at the discount autopart stores? I have read that the stringent regulations concerning r-12 to r134a conversions only apply to the a/c shops and not to the do-it-yourself crowd. I do not want to mess up my a/c muffler fittings with the 134a adapters. Thanks

Tom73

My understanding is that all 134a stuff has different fittings then the R12. Done so you will not mix them up. The can has a different type of fitting so the R12 hoses do not work. You will also need to install 134a valves on the shrader (sp) valves that are currently on your car.

tom...

The Gooch

:iagree: just did this to my '84. Your post wasn't clear about whether you bought a new/refurb. compressor, new condensor, cleaned out your a/c system, and replaced with new washers. The oils from R-12 and R-134 are not compatible and will eventually degredate your entire a/c system.

R1234

Thanks all for the replies,
I have new ac lines (using the original style clamps with positioner tang), ac muffler, o-rings, expansion valve, original style POA valve that I acquired that is supposed to be in good working condition, drier bottle and condenser. Still using the original evaporator and the compressor is the original style that I took to a local mechanic who rebuilt it using the ceramic bearing and seal. The original evaporator has been flushed with ac flush and I have added 11oz of ester oil to system. I have been advised to take the schader valve out lowside connection at the POA valve and put the 134a connector at this location. At this location the adapter will be kinda out of sight and I can charge the 134a at this connection. Leave the original style connectors on the ac muffler and use r12 gauges to check highside/lowside pressures. Does this sound about right? I plan on keeping this car and doing most of the work on it myself so I'll know what type of freon is in it. I just want the conversion as less intrusive as possible.

GregP

A R12 cycle compressor will not work efficiently with R134, they are desigend for different pressure cycles. There are several R12 direct replacements available now that would be a better switch than the R134. Do a search or talk with a good local AC person. Tony (Tony's Corvettes) did a R&R on Julie's '70 AC system and used one of the new R12 replacements and it works very well (so well it actually froze itself up once).

-Greg

R1234

I keep getting different feedback on the use of 134a. Some say it cools just as good as R12 but has to be charged at just the right amount and others say it does not. I thought about at least trying 134a to see how it works.

Has anybody used Freeze12? It's supposed to be direct r12 replacement.

phrogs

I have heard the freeze 12 is crap!

Im converting my ZR-1 to r134 so as long as I get something out of it ill be happy!

johnny

Tom73

Freeze 12 is 80% 134a, so may as well go for 134a.

tom...

LemansBlue68

R134a requires a different lubricant (glycol based) than R12 (petroleum based). Make sure your compressor is compatible with R134a type lubricant. I've seen adapters that will bolt on your R12 fittings so that you can charge with R134a. The pressure cycles are not that different for the two refrigerants; the prime difference is compatibility of the compressor with the lubricants. Generally an R134a compatible compressor will work with R12 but not the other way around. R134a also will diffuse through rubber hoses and seals where R12 won't, although I wouldn't be overly concerned with using your R12 gauges and hose sets to fill with R134a (if you can work around the fitting incompatibility).

I'd also try to get more vacuum than 24 "HG. Any air in the system acts as a volume reduction in the system (like putting a large brick in your toilet tank or taking a few rows of tubes out of your evaporator). It also is not enough to assure that all the moisture is evacuated (you want the vacuum to be well below the vapor pressure of water at ambient temperature). See if an A/C place will pump your system down for you, drive the car home, and fill it yourself. Better yet, borrow a vacuum pump. Heck, Michigan's not that far of a drive for a break in the summer heat! I'll loan you mine!

I've also heard that some of the "flea market/swap meet" R12 "compatibles" are hydrocarbon mixtures (as in propane mixes) that are NOT NON-FLAMABLE. You definitely don't need a blow torch in front of you if (god forbid) you are ever in a front end collision.

This is entirely perception on my part but I still think the R-12 systems cooled better than the new R134a systems.

Good Luck. Glad to hear the A/C system is coming together well!!

Check out http://www.imaca.org. They have information on R12 to R134a conversions (although they won't tell you things that you can get away with if you don't want to follow the EPA guidelines to the letter).

phrogs

What kind of vacum system do you have or can you recomend that is realtivly cheap.
I have seen a few on ebay, Im going to do my own converion on my ZR1 have all the parts in route but I might just have a A/C place vacum my system.
and with vacuming will that remove all the old oil from the system
thanks!

johnny

R1234

Eric, Thanks for the offer and advice. A friend of mine at work offered to loan me his Robinair vacuum pump. I am using ester oil.
I'm going to work on the ac system some more this weekend. Even if the 134a doesn't quite work as well as the 12 maybe it will at least allow me to check the ac system out for leaks and proper function of the other components. When I'm satisfied that all is well with the system I can go with r12. :chevy

LemansBlue68

My father-in-law is a retired sales rep from a company that specialized in ultra high vacuum equipment and helium/halogen leak detection equipment (No, he wasn't a Kirby salesman :jester ). He gave me a Sargent-Welch vacuum pump a few years back that was a demonstrator that he used on the road when he replaced it with a new one. This baby pulls a major vacuum!!! I use it for A/C work which is kind of like shooting butterflies with an elephant gun. I'm not an A/C technician by trade (I'm an engineer) but I do a lot of stuff on the side for friend's home and auto. I got in to it because of dealing with too many dishonest or incompetent A/C technicians. I don't trust anyone to do my A/C work now. There's good guys out there, but I guess just like every trade there's bad ones too.

R-12 is just too expensive to waste these days and it's very illegal to vent it. Fortunately, I haven't dealt with too many of these lately. I don't have a refrigerant reclaimer, but have thought about buying one. For some reason, all the units I have worked on recently have already leaked all their Freon out ;) .

R1234

I put the 134a in the system. The 68 a/c system calls for 52oz of r12.
I charged the system somewhere in the neigborhood of 85% or 44-45oz of 134a. All components seemed to be working as they should. When turning the a/c compressor on the idle would drop slightly. The evaporator tubing at the expansion valve temp. probe was nice and cold. Condensate from evaporator running from drain and puddling nicely. The temperature here today was 90 and humidity high with rain showers.
The low side pressure is 26 and the high side is 250. This is at 1050 rpm idle.
I didn't have a good thermometer to check the air temp. out of the center vent but it was nice and cold. I'm going to get a thermometer tomorrow and post the temp. With the windows up you could feel the nice, cool temp from the inside leaking out around the windows at some weatherstrip locations. I'm going to have to fix that. Amazing! It has been a good day for this novice! I guess time will tell how the system holds up. :chevy

A C

http://www.robinair.com/acsolutions/.../presstemp.htm

You are just a little low in your evaporator pressure. That is below freezing and your coil will ice up if you take a long drive with the A/C on. Your head pressure seems ok since the temp was 90 or more. I think another ounce or two and you will be all set. :cheers:

3X2-427

Hi Tom;
I have done this conversion several times using the stock R12 valving and compressor components without difficulty. I understand the laws as you; the professional AC shops are required to change the valves. My 69, (now belonging to Dr Rebuild was a visually stock system but 134 charged. I found it more than sufficient but Doc felt it wasn’t up to his requirements and changed it back.
The valving adapter can be rigged from auto store components readily available
Good luck
jer



[Modified by 3X2-427, 10:28 AM 8/4/2003]

R1234

The thermometer reads 62F at the center vent with ac on max and fan set to high. Looks like I'll need to do a little more fine tuning to lower temp. My 1990 chevy truck has also been converted to 134a. Temp. at center vent 45F.

Smokehouse69

An A/C guy on the C3 Forum stated that the ideal pressure for the suction side was 26 to 28 at 2000 rpm. Anymore than that idicates an overcharged condition.
Another alternative to R12 or R134a is Enviro-Safe, it is hydrocarbon based and therefore I don't think it is on the DOT's approved list of automobile refrigerants but it is approved in many other countries. It is also found in many refrigerators, freezers, watercoolers etc, that are used in our homes and offices.
I'm going to put it in my 69 and see how it works.

http://autorefrigerants.com/co00033.htm

R1234

Yes, I read that also. I'm going to play with it some more this weekend. Maybe I can get the vent temps down.

Larry B.

I may have been the person that posted the 26-28psi. That figure is from the temp/pressure chart of R134a. vs. the same temp of R12. At 30 deg.F the evaporator pressure would be 28.5 for R12 and 25.6 for R134a. That would be with everything 100% which is rarely the case. R134a does run a little higher head pressure so I prefer the lowest pressure possible. I run my stock 69 with R134a at 26-28 psi at the suction port on the compressor and it never freezes up even in the humid SE. There does seem to be a little "black majic " involved when getting a R134a conversion to work just right. This car is fine but I have seen others not do as well. Experiment..

R1234

One thing that I have discovered that's causing my vent temps to be warmer is hot air getting into the duct. I can feel a noticeble amount of hot air coming out of the vent when the system is turned off. I need to track this down. Could be the heater valve not closing all the way or engine compartment heat or both. :smash: