r-12 to r-134a conversion questions

[shyguy164]

I'm looking for people who have done the conversion or had someone do it for them or if you just have general knowledge of the subject.

 

After any residual r-12 was "recovered" by whatever means were used, what parts of the system were replaced? Orifice tube? Accumulator? Was the oil changed? If so, how was all the old incompatible oil removed? How long has the system been functioning properly since the conversion? Did you change the compressor control valve? Thanks in advance!

[Crazy K]

I always open up the system and replace ALL O-rings and the orifice tube (filter) cost? less than $10.

 

 

I want to learn about freeze 12. it supposed to be much better than R134a.

 

Brian P? Are you the go to guy for freeze 12?

[shyguy164]

so all you do is o-rings and orifice tube? no oil change or accumulator? how have your converted systems been running and how long? i'm sick of topping off my r-12, it's getting expensive. i've got a 30 lb cylinder of 134a, so it's technically free since i bought it 2 years ago.

[mfewtrail]

The accumulator should be replaced in a "proper" conversion.

 

Ken, Freeze 12 isn't really any better. I've said it before and I'll say it again: There are NO drop-in replacements for R12 EXCEPT R12. You should technically do everything that you would do when converting to R134a if you want to use freeze 12. Freeze 12 is 79% R134a after all(it's a blended refrigerant, I forget what the other refrigerant it's blended with is...a quick google search would give you that info). Even though I said there are no drop-in replacements = doesn't mean that you will have a problem if you use it as a drop-in. Use it at your own risk though...

 

I've seen people saying that Freeze 12 cools so much better, but the tests that they concluded this information from were on TWO different vehicles. Freeze 12 is on par with straight R134a from my experience with it. It's kinda like the difference people state between R12 and R134a. In a properly working system, there's not really going to be a discernable difference. I've measured vent outlet temperatures as low as 35-36*F in my TGP with R134a and my TGP with R12 for what it's worth. Even though our cars weren't designed with r134a in mind, they work very well with it.

 

EDIT: I also forgot to mention that R134a is a bit cheaper than Freeze 12. Freeze 12 is about $11-12 per 12oz can in my area. R134a can be had for $5.97 per 12 oz can...or cheaper if you find it on sale. Big Lots just had a $4/can sale a while back and I stocked up. If you have a Big Lots in the area, it might be worth stopping by to see if they still have any. The sale was a few weeks ago, but my local store still has 100+ cans left that are still being sold at the same $4/can price.

[Addicted To Boost]

I have a few new cans of Freeze 12 sitting here that I'm not going to use (I'm moving in a couple weeks). PM me if you're interested.

[BIGBULS]

I just think it's funny that R134a is like the only thing (automotively) that is going DOWN in price.

 

Shit, it's only $7.50 a pound now (list price), and I work at a stealership...........

[carkhz316]

Like the others said, O-rings and probably, orifice tube, though I didn't reaplace the orifice tube, or the accumulator. Also, both the high and low side fittings are different, which have to be replaced. I retrofitted my 91 Euro a little over a year ago, and it still works great. After recovery, we put a vacuum pump on it for awhile, and pulled it down to like 30 hg, which allows any moisture to evaporate and be pulled out. This also verfies whether or not your system has leaks, to an extent, for it could still have a leak under postive pressure. Then, as per service procedure applicable to your vehicle, fill with proper charge of oil (PAG, I think), and proper charge of R-134a. On a side note, if you've been "topping off" your refridgerant lately, I would definitely check for leaks, via a UV leak detector, or a "sniffer". I know that the compressor shafts seals like to go, as I've done a bunch of thise lately. Hope this helps

[Crazy K]

allegedly... the difference is the amount of pressure in the system. R134a is much higher in pressure and may contribute to excessive compressor wear. freeze 12 is closer to the R12 pressure and thus less likley to wreck mechanical havoc... in theory.

 

 

the reason that the R12 cars take to R134a so well, is that the system is the EXACT SAME SYSTEM THROUGHOUT except for the service ports. However, ALL the cars i have that were originally equipped with R134a seem to have developed compressor related issues. they all making various hammering noises and the like.

 

 

ALSO I have done the R134a conversion maybe 6 or 7 times... (actually... I have done this many rebuilds but some were previously R134a equipped cars) whenever i can... I completely dismantle the entire system. Drain EVERYTHING of old oil and refrigerant, spray parts like the condenser and evaporator though with high quality brake cleaner and allow to dry. I physically remove EVERYTHING!

 

When i reassemble i use the correct oil for a 1995 R134a equipped W-body. I take the compressor, lay it face down and pour the proper oil in the port on the rear and turn it. as I do so I figure out which is the inlet (usually has a mesh catch screen) and continually pour while turning the compressor. I stop when oil has come out of the outlet port and make sure all bubbles have come to the surface. I now have a fully lubbed compressor.

 

I also coat all new O-rings with Dielectric grease, and stick in a new orifice tube.

 

I do something bad as well... i put in the first can of R134a and run the system for a while, to see if it holds pressure. once it has worked for a while and the system has not leaked... I vent it. then i re-fill the system with 2 cans and that usually tops it right off.

 

 

 

back to task... I think it takes alot more R134a to make a good functioning system than R12, leading to higher operating pressures and wear. I need to learn more to determine if Freeze 12 is an excellent alternative.

 

 

 

otherwise... what I have done:

1975 buick: converted... compressor was bad. -never fixed-

1969 buick: converted lost charge in 24 hours. -never fixed-

fiend's 80's jeep. converted but leaked out in 2 hours. -never fixed-

1992 lumina converted one week after buying, drove 50,000 problem free miles, with no further service. still had a good charge when dismantled.

1995 CS: new O-rings and orifice tube. Compressor now makes grinding noises and the charge lasts about 2 years.

1991 vert: Conversion. new O-rings and orifice tube. system has never been charged.

1994 CS: new O-rings and orifice tube. Compressor makes hammering noises but never got worse. 85,000 miles with only one can added last year.

1992 vert: Conversion. new O-rings and orifice tube. system has never been charged.

 

not by me... but one of mine:

1995 ciera. needed a compressor. it has making hammering and grinding noises.

 

and... the 1993 vert was still R12 charged last time I checked. -might be dicharged now, the a/c did not work last week-

[jake63]

I did this on my 1990 chevy truck years ago, didn't change any o-rings or the orifice tube, just the high and low fittings that came in the kit. Simply filled the system with 134A and oil charge and it's been working for years. I did have to replace my high side valve once because it leaked but no other issues. Done it to a few other cars with no issues. However, changing the o-rings and tube is not a bad idea and they are cheap.

[GutlessSupreme]

How to do it properly:

 

http://www.honda-tech.com/zerothread?id=1665946

[Crazy K]

How to do it properly:

 

http://www.honda-tech.com/zerothread?id=1665946

very good info. I have been unable to rent the vacuum pump myself, as the AZs near me can't find it.

 

If you notice that the 91 and 92 verts have had they systems freshed up, but have not been charged... it is because I tried to locate a vacuum pump to refresh their systems. Someday I will.

[GP1138]

Right now my system has a major leak. I charged it and was blowing cold air, and the next morning, I had nothing. I suspect a leaky valve core.

[Crazy K]

Right now my system has a major leak. I charged it and was blowing cold air, and the next morning, I had nothing. I suspect a leaky valve core.

I'll help you redo it when I get there.

 

 

[carkhz316]

Just 2 things about the post on the Honda site. The caps on the high and low side valves are the same as a valve stem. They DO NOT seal for leaks from the valve. They simply keep dirt and debris out. That's it. Secondly, if starting out from scratch, there is an easy way to know exactly how much to fill your AC system with. Usually there will be an underhood sticker (Warning/Caution style) about the AC, and it will typically say how many pounds and ounces the AC is supposed to be charged with. Otherwise a service manual, and/ or All Data or Mitchells on Demand will have this number. Then, if you have access, which the guy on there went to good lengths to get the Vacuum pump and such, then there should be a way to get a "AC keg scale" which will weigh the amount of refrigerant that you put into your vehicle. Just wanted to point out that is how you can accurately charge your AC

[1990lumina]

This is how I do A/C work while i'm at work

[1990lumina]

Just 2 things about the post on the Honda site. The caps on the high and low side valves are the same as a valve stem. They DO NOT seal for leaks from the valve. They simply keep dirt and debris out. That's it. Secondly, if starting out from scratch, there is an easy way to know exactly how much to fill your AC system with. Usually there will be an underhood sticker (Warning/Caution style) about the AC, and it will typically say how many pounds and ounces the AC is supposed to be charged with. Otherwise a service manual, and/ or All Data or Mitchells on Demand will have this number. Then, if you have access, which the guy on there went to good lengths to get the Vacuum pump and such, then there should be a way to get a "AC keg scale" which will weigh the amount of refrigerant that you put into your vehicle. Just wanted to point out that is how you can accurately charge your AC

 

They do seal seals - but they only seal leaks if the low side was ever to go into a vacuum the schader valve could get pulled down - this is what the cap seals

[GnatGoSplat]

I had the 89 and 88 changed over simply be removing the R12 and replacing with R134a at least a decade ago.

The 89 gets ice cold like before. the 88 didn't.

I don't know why. I guess sometimes you get lucky.

 

[shyguy164]

Just 2 things about the post on the Honda site. The caps on the high and low side valves are the same as a valve stem. They DO NOT seal for leaks from the valve. They simply keep dirt and debris out. That's it. Secondly, if starting out from scratch, there is an easy way to know exactly how much to fill your AC system with. Usually there will be an underhood sticker (Warning/Caution style) about the AC, and it will typically say how many pounds and ounces the AC is supposed to be charged with. Otherwise a service manual, and/ or All Data or Mitchells on Demand will have this number. Then, if you have access, which the guy on there went to good lengths to get the Vacuum pump and such, then there should be a way to get a "AC keg scale" which will weigh the amount of refrigerant that you put into your vehicle. Just wanted to point out that is how you can accurately charge your AC

 

They do seal seals - but they only seal leaks if the low side was ever to go into a vacuum the schader valve could get pulled down - this is what the cap seals

 

Plastic caps never work well for sealing refrigerant leaks. Brass caps with gaskets, on the other hand, work quite well when properly tightened. The schrader valve can not get pulled open by vacuum or pressure, that's why they're used in refrigeration.

 

Ken, how long have your converted systems been running without pulling a vacuum first? I've always read and been told/taught that if there's air in the system, it gets compressed and the moisture in the air condenses and reacts with either the oil or refrigerant to form an acid the eats the system from the inside out. I'm lucky enough to have a big vacuum pump available for use for my a/c needs.

 

So my conversion is complete (so far). I changed the orifice tube, vacuumed, and charged with 134a. However, my vent temp was only 58*F. Plus the air flow seemed to be more restriced now than when I bought it 7 years ago. 4 hours later, I had the evaporator removed. Take a look at the pics. The first is the fan side of the evap. The second is of the back side. This is why they use cabin air filters now! Dummies. After cleaning the bastard, reassembling, vac-ing, and charging, i've now got a 48*F vent temp. I'm still thinking of tweaking with the charge a bit, cleaning the shit out of the condenser, and possibly replacing the accumulator.

[GnatGoSplat]

One thing that might also make a difference is that little valve in the compressor. It's different for R12 and R134a. I forget what it's called, it's a little aluminum thing held in with a snap ring.

 

[carkhz316]

Can't remember what it's called either, but it's something to do with making it a "variable displacement compressor"

[GnatGoSplat]

Yep. It's apparently the only difference between an R12 and R134a compressor. When the 94 wasn't cooling worth a crap, I posted on an A/C forum (too many years ago to remember the URL), but the guys there said to replace that thingamabob. I replaced it and the result was ice cold air... till a bearing went on the compressor!

 

[shyguy164]

I know it's "recommended" to replace the control valve when converting from r-12 to 134a. I don't think there's any difference between the compressors though. Changing that valve would help if it's clogged. Isn't there a suction screen in the compressor too?