How to: Converting an R-12 Air Conditioner to use R-134a

[Glacier991]

ok do u have to chnage the oil if u swtich to 134a i have heard dif things

I think that's covered in this long thread, but your short answer is yes. Flush the system and use ester oil would be my recommendation.

 

[Scott B.]

Should I change to R134a?

Great info!

But my question is, in my '93, my A/C (R12) works fine. Should I convert to R134a just to do it?

At some point in the future, I will replace the engine. Since I will need to open up the A/C, should I change then? BTW, I have 3 cans (12 oz.) of R12 that I bought many years ago ($2 a can!).

 

[V8BoatBuilder]

Great info!

But my question is, in my '93, my A/C (R12) works fine. Should I convert to R134a just to do it?

At some point in the future, I will replace the engine. Since I will need to open up the A/C, should I change then? BTW, I have 3 cans (12 oz.) of R12 that I bought many years ago ($2 a can!).

Don't open an A/C system unless you have too, why spend the $$$. A proper conversion isn't cheap. However, when you pull the engine, you will need to discharge your A/C system. If it's open to the air for a while, you'll also need to change the accumulator as it contains a dissicant that will quickly be ruined by ambient moisture.

Since you have R12, it's a 50/50 whether to stay R12 or convert to R134. If it was me, I'd convert. By evacuating the system and replacing the accumulator - you've put in most of the hard parts necessary for a proper conversion. It will save time and $$ down the road, if you need to work on the A/C system again.

 

[Glacier991]

On this point I respectfully disagree with my good friend V8Boatbuilder. IF you do not have a need to, don't convert. IF you have enough r-12 to STAY r-12 after repairs (and you do) STAY r-12. Those systems were designed around r-12 and work best using it. 134 conversions tax the condensor's capacity to get rid of the heat - 134 designs have a bigger condensor. Me? I have a 92. It is r-12. I totally rebuillt it a few years ago and it's r-12. Hasn't lost any refrigerant so far... if I replace the system ever again? r-12 for me.

It helps to have r-12 available to you. You have some. So my advice is... stay r-12.
(regards to Aaron - there's no right or wrong answer here... just opinions.)

 

[Scott B.]

Thanks for the opinions - I think I will stay R12. I understand the reasons for converting, but I do have some "extra" R12.

Is the factory condensor sized OK to function properly with R134a? I had heard that a true 134a condensor needed to be larger. This has to do with the properties of 134a (vs. 12). If so, I would assume the evaporator should be larger too, right?

 

[F1JQM]

HI there!
My '92 Eddie Bauer compressor just blocked, I plan to retrofit it to R134a. It has been previously charged with R413 (as here you don't find R12) which is in Europe the best solution if you don't retrofit (but most expensive: about $200 for upload at an A/C automotive specialist).
Shall I discharge securely this R413 by myself (and how) as the compressor is completely blocked, the clutch blown away, and my Explo blocked in front of my garage door with a bad A/C belt??? (headaches: I don't want to burn away the old bet and destroy engine, but I don't neither wanna use the brand new I've just bought from Ford...)
I will change compressor, clutch, filter, valve and evaporator, then replace the belt and go to the next equipped garage to have a vacuum and reload...
what a program!
Thanks for you reply, Olivier

 

[gijoecam]

Indeed, V8's justification is sound, but on my '93 Ranger, it boiled down to dollars and cents: Let's weigh the options: a $700 rebuild that may or may not hold a charge for the summer, or a $30 conversion that may or may not last through the summer? If the $700 rebuild doesn't last, I'm out at least another $150 in R-12 to get it fixed. If the R-134 doesn't last, I'm only out another $30 on top of the conversion.... I took my chances, and it was well-worth the investment. I had a leaky replacement schraeder valve two days after the "conversion". The shop I bought it from threw in the replacement R-134 for the second re-charge because the valve failed. It ran for three more years without a problem after that.

Preach all you want about the "right" way to do it, and from a mechanical standpoint, I'll agree with you 100%. But at the same time I'll swear by the conversions every time. The benefit doesn't justify the cost for me.

-Joe

 

[F1JQM]

by the way, could someone tell me how much R134a I have to charge once retrofitted? Prevoiusly, it was 0.750 kg R12 (said on the label...)

 

[RiverRat]

Around here some people drive south of the border into Mexico where R12 is inexpensive. Are there any countries near you where you could get the work done cheaper? Going south for some surfing, lobster and R12 makes a pretty good weekend.

 

[Glacier991]

On a conversion it is not a bad idea to start with 75-80% of the R-12 charge when converting to 134 and start checking vent temps and presures then go from there. Some will tell you add 60%, others say add 80% etc... 75% is a good start and feel your way along from there is my advice.

 

[Glacier991]

gijoe, I am not in disagreement with you. I apologize for sounding "preachy".

 

[gijoecam]

You didn't sound preachy.... well, maybe just a little bit at first. I can't argue your point about the mechanics as you are 100% correct and I'm 100% in agreement with you on it being the true "right way" to do it. I found a fairly successful alternative that worked for me and, while it's not exactly "according to Hoyle," it may help others in choosing the best option for them. I make a fairly decent living, but I'd be hard-pressed to fork over $600+ when a $30 fix might work almost as well. Sure, it might not work quite as well as the total retrofit, but for $30 on a car that's only worth $3000, it sounds like a decent enough deal. I also looked at it this way.... sure it's not as efficient as a full conversion or as the R-12 it replaced was. Say it only works 70% as well as the R-12 system.... that's only a 30% reduction in efficiency, and still a full 70% better than it was working after it failed. Again, for $30, it's worth a shot, for sure.

I certainly wasn't looking to pick a fight or anything either.... Just sharing my opinion on the matter too.

-Joe

 

[Glacier991]

No offense taken. Sharing honest intelligently thought out opinions is what makes this board such a great place. You have already established your credentials in my book as someone who knows his stuff. Thanks for adding to this thread. You point of view is certainly a valid one!

 

[shawnasexplorer]

retro ac

my ac was retro to 134.my problem is my husband change the ofice tube.now my dryer freezes up and he says my low pressurer is very high and the compressor doesnt cycles off.but on a hot day my temp threw the vents runs about 50 degrees.he is going to replace the cycle swithch and add a little more r134.is this a good idea.

 

[Glacier991]

when you say your dryer is freezing I am assuming you mean your evaporator. The low rpessure cutout switch is designed to prevent this by cutting off the compressor when the low side pressure gets to a oint where the evap temps could cause it to freeze. Replacing this switch is a good idea if your low side gets below 25-27 psi and the compressor continues to run. Not sure what he means when he says low side pressures are high.... since refrigerant pressure has an equivalent temperature, high pressures in the low side of the system would not be likely to produce temps sufficient to freeze your evaporator. I doubt your low side is high, I suspect the cycling (low pressure cutout) switch is your main culprit. From here I cannot really comment on the charge state.

 

[jrhartman]

******AC noob question alert****

how can I check to see where exactly my system is leaking? I know my way around the garage/toolbox but I have never worked on a AC system

thanks

 

[Glacier991]

Sometimes you will see an oily stain around a leaking fitting, but not usually. You can either add UV dye to the system and check it with a blacklight, or use an electronic halogen detector (I refer to these as sniffers). You can also use an old style "sniffer" which used a propane torch (color of flame changes). Best and fastest? Sniffer, easiest ? blacklight.

Check your accumulator, these had a tendency to rust under the styrofoam "blanket" and leak. Make sure you have caps on the high and low side fittings.

 

[Rhett]

Good thread. Interestingly, I have not seen the proper low-side psi numbers for an R-134a-equipped a/c system in this thread. Maybe I have missed it?

I also have a question re: my truck's a/c, and I think this is as good a place as any to ask it.

1) Is the low-side pressure the same for *ALL* R-134a systems, no matter the vehicle?

2) My truck is down to about 20 psi on the low-pressure side compressor off, when idling, doors open, a/c on max. Cycling seems normal to me, and during the compressor ON cycle the psi rises past 30 psi, but then drops to 20. The lines are not very cold, just cool to the touch. On an ambient air of 82 degF the system could only generate 54 degF air, even driving at 70 mph. My understanding is that I should be seeing 40 to 45 degreeF air on such a day. I conclude that I am due for a R-134a charge. Is this correct thinking?

 

[Glacier991]

On a fixed orifice valve system such as FORD uses, the low side will draw down as the compressor operates. Since pressure equates to temperature, to avoid freezing the evaporator, the system has a low side cutout that stops the compressor operation when the low side falls to that predetermined point (around 25-27 PSI.) The system off, high side and low side start towards each other, equalizing until the low side is high enough to allow the system to commence operations again. The cycles continue, their frequency based on a number of factors. On - Off - ON - Off.


If you find your compressor is cycling frequently, it is a good sign you may be low on refrigerant charge - it doesn't take long for the compressor to move out the refrigerant since it's low, and the low side comes down pretty quickly, hence the quick on/off cycle times. In a properly charged system you should expect 1-2 cycles per MINUTE. (Summertime temps of say 80 to 85 degrees outside).

High side in such a system will have pressures that vary, depending on condensor efficiency, airflow, ambient temp etc. In other words it's not like putting or checking air in a bicycle. They will vary. There is no absolute "right" pressure.


Hope this helps.

 

[Rhett]

Yes, it does help, thank you a lot. I was aware of the basic operation of the system but you can never learn too much . I believe I'm getting at least 4-5 cycles per minute and the tubes are not as cold as they should be.

My understanding is that the thicker tube leading back to the compressor should be a little colder than the thinner tube. Neither of them are as cold as they should be.

Is an R-134a system a "closed" system? In other words, assuming all the o-rings and seals are working, no refrigerant should be escaping, if it's truly closed. Therefore, how can the R-134a need charging UNLESS it is leaking? Or does the refrigerant simply deteriorate/break down over time? If it deteriorates, what is it replaced with, plain air?