ehall

Every single summer, we end up with a boat load of posts asking about compressors, refridgereants, fittings, tools, oils, and compatibility with various refridgerants, stop leak,etc. I think we need to creat a thread that addresses all of the various aspects of keeping up with 951 AC systems. Clarks-Garage is great for a lot of things, but it is pretty minimal on AC systems.

So let's start with some general rules.
If you don't know an answer, ask the question here.
If you don't know the answer, DON"T answer a question with a guess, or any sentence that begins with, "I heard that"...unless it's followed by a question such as, "is that true or not?"
If you don't KNOW, don't answer.

So here are some questions to start.

What oil/s are compatible with R12?
What other refridgerants are compatible with R12?
What actually happens when an incompatible refridgerant or susbstance is added to an AC system?
Aren't pressures dependent upon ambient outside temps?
Do "stop leak" agents cause the same potential harm to AC systems, as similar "stop leak" agents can cause to other systems, such as power steering or engine oil?
Is the debate over flammable refridgerants a valid argument? Why or why not?
What refridgerants are compatible with R134A?
What "oils" are used with R134A?
What refridgerants cool more efficiently than R134A?
What risks are associated with those alternatives?

We need a list of all of the auto AC refridgerants available, and their pros and cons.
Please list any that you can think of.
That's a start.
We probably should list DIY tools and parts needed for maintenance or repairs, as well as best sources.

CurtP

Here is a link to the EPA's R134a conversion: http://www.epa.gov/ozone/title6/609/.../retrguid.html
They do touch on oils, but they don't make a recommendation on PAO or esters, just that there's differences. They do hit some important topics, like barrier hoses and O-rings.

Here's a link to EPA's hydrocarbon FAQ: http://www.epa.gov/ozone/snap/refrig.../hc12alng.html


I personally went with R134a because it's inexpensive and readily available. My 951 cools well with the conversion in my climate. One thing that I did was to use a set of gauges to determine system charge instead of weight. Normal range for a R134a system is 25-45psi. On my car, 25psi was too low and 45psi was too high. I got the coldest air from the ducts at 30-35psi.

ehall

bump

KuHL 951

Just call Griffiths, they have all the answers you are looking for and will do you right.

ehall

This thread isn't really a thread for me or any issue I have with my car. I was hoping to use it as a general AC thread, that answers as many questions as possible and gives future folks a sort of "one stop" info source.
There are a huge number of somewhat related AC threads, but it takes a really long amount of time to sift through the weeds to find the info that one might be after. Hopefully we can create a thread that answers as many questions as possible, right here.

sm

Q: What is a good internet A/C resource?

A: Without a doubt, this forum: http://www.autoacforum.com/. Those guys know A/C and work on them everyday. Just tell them your problem, your car, and they will likely be able to help.

ehall

good post. Thanks.

Synth

I've got a couple questions for the experts. I have a 86 951 that I've been overhauling the motor on. The AC looks to be completely original and I'd like to update sometime in the future. My question is:

What is recommended to bring the AC system up to date? (what should be replaced? what should be updated to a newer style part? Any thing that should be added?)

what is the bare minimum for a functioning AC system, and what is required for a great system?

And finally what are the costs associated?

Thanks in advance!

dacula951

I'll give it a go:

What oil/s are compatible with R12?
There are basically 3 types of refrigerant oil: good old mineral oil used with R12 for eons, and the 2 synthetic oils PAG and POE developed for use with 134a. If using R12, I would highly recommend sticking with mineral oil. The synthetics, especially POE, do not lubricate as well and both synthetics (especially PAG) are hygroscopic (absorb water).

What other refridgerants are compatible with R12?
Not sure of the reason for this question. Many other refrigerants can coexist with R12, but mixing refrigerants is not a good idea. And you especially wouldn't want to contaminate R12 because using it in pure form is what our cars were designed for and work best with (some may dispute this by arguing that some blend or hydrocarbon refrigerant works better. Even if this is true they have disadvantages that R12 doesn't have).

What actually happens when an incompatible refridgerant or susbstance is added to an AC system?
Usually the only harm is bad performance, but in the case of lubricant it can be damaging. For example, if the mineral oil were left in place and no PAG or POE oil added in a R12 to R134a conversion, the mineral oil not being miscible with R134a means the mineral oil may not be carried back to the compressor and starve it of oil. If moisture is the "substance", it can cause poor performance (by freezing and causing blockages) and can be damaging (causes acids to form). Air in the system decreases performance and it's inherent moisture content can be damaging.

Aren't pressures dependent upon ambient outside temps?
Refrigerant sitting in a sealed can follows a temperature/pressure curve. The higher the temperature, the more refrigerant liquid will boil off and increase the pressure. The low and high side pressures in an A/C system are influenced by a lot of factors, temperature being a big one.

Do "stop leak" agents cause the same potential harm to AC systems, as similar "stop leak" agents can cause to other systems, such as power steering or engine oil?
Never used them and likely never will. I prefer the old fashioned approach of just fixing a leak and not taking any chances.

Is the debate over flammable refridgerants a valid argument? Why or why not?
I won't offer an opinion here.

What refridgerants are compatible with R134A?
Again, not sure of the reason for this question. Most prefer to use 134a in pure form. If you're searching for better performance than pure 134a in an older system, I'd recommend using a blended refrigerant rather than mixing your own. The main disadvantage of blends is that with a slow leak certain components of the blend will leak faster than others, resulting in degradation of the blend over time.

What "oils" are used with R134A?
Only POE and PAG is compatible for use with R134a. There's debate about the need to remove the mineral oil when retrofitting to 134a. In my opinion, it's best to remove as much mineral oil as practical (at least drain the compressor and change the filter/dryer). As for which one to use, PAG or POE, OEMs frequently recommend an oil type in retrofits on their vehicles. When replacing a compressor with a new or rebuilt unit, the instructions may specify the oil type. Early on, POE was thought to be more compatible with residual mineral oil and was therefore preferred in retrofits. The concern that mineral oil is incompatible with PAG has proven untrue, so it seems a shift to PAG has occurred. PAG is more hygroscopic than POE but evidentially this is outweighed by it's better lubricating properties.

What refridgerants cool more efficiently than R134A?
In our cars, the answer is R12. I would recommend sticking with it if possible since our cars were designed for it. If I were forced away from R12, I'd probably convert to pure 134a, but that's just me.

What risks are associated with those alternatives?
A big disadvantage is future serviceability. Many shops won't want to touch it if they know anything other than a pure R12 or R134a is in the system. Another risk is performance that doesn't meet expectations and degradation over time as certain blend components leak faster through small leaks.

Zero10

I'd like to offer some more semi-fact-opinion comments up here. I don't want to sound like I am trying to push a specific product, but I'd like to share my experience with one particular refrigerant.

I have always used R12 replacements in my air conditioning systems. If you are not replacing the compressor, condenser and possibly the expansion valve, it is not worth filling your R12 system with R134a. It simply won't work right and you will never be happy. Proper R134A conversions are excellent, I have seen a number of them done very well but they often carry a rather high price tag and are not terribly DIY friendly.

I prefer to use hydrocarbon based R12 replacements for this reason, my personal favorite is Red Tek since they add a tracer to it so you can detect it with a R12/R134A sniffer, although other popular ones are HC12 and Duracool. Freeze-12 is different and I cannot comment on it very much. People rant and rave about the "flammability" of these products, however all of the MSDS sheets I have ever seen place the flash points and other relevant fire data for these refrigerants EQUAL or HIGHER THAN R134a.

I also know that these refrigerants carry more heat per unit volume than either R12 or R134A and they work perfectly well in R12 compressors. I strongly caution against using these refrigerants in R134A systems unless you have a variable displacement compressor since you will likely have a freezing-up issue on your evaporator.

These refrigerants make it very easy for a DIY'er to repair their own system since they are not adversely affected by small amounts of moisture or air in the system, in fact, red tek says if you don't leave air in the system it will over-cool and you will have a freezing issue with your evaporator. I have never personally have this happen, but it is their warning and while trying to be factual and objective I should pass this on. If you have moisture in a R12 or R134a system it will produce powerful acids that can cause very serious damage to your A/C components (expansion valves, compressors, etc.).

The general procedure to convert to Red Tek is to evacuate all other refrigerants from the system and drain the oil from the compressor and condenser (or if your system has been open / missing pieces then maybe you don't have to worry about this step), then repair any known/found leaks, replace the receiver/dryer and fill with Red Tek. They produce a kit that has 2 cans of refrigerant (including oil) and a charging hose with a low side pressure gauge. I realize this doesn't give you your high side pressures, and after charging the system I strongly recommend having somebody with a high side gauge verify the pressures are normal on that side as well. I prefer to use this kit, or buy the specific cans from this kit since they include oil, but it can also be purchased in 20 or 25lb cylinders for use in commercial charging equipment where you add your own oil.

I have used this in both my past 944 and my present 951 and the results were exactly the same, bot had completely original R12 systems. Once I'm moving (i.e. not sitting in my driveway idling) I get vent temps of 1-3*C, as the compressor cycles on and off it moves within that range. If I am sitting still the temps rise up to 5-8*C. I have been told this could be due to my system being slightly over-charged and I although I am not an expert I am still working to correct this. Take my vent temps with a grain of salt since I am not an expert and they are not necessarily a hard and fast rule of what you will get.



Sorry if I sound like a Red Tek fanboy, I should also note that Duracool produced exactly the same vent temps, however since I couldn't find it with my sniffer and it all leaked out on me I switched to RedTek and finally found my super-elusive leak.

spanky

Thanks for the info.

ehall

That's all good stuff. There are all sorts of sources of sketchy info on this topic, and there are opinions all over the place. The whole point of this thread is to help clarify and dispell info and misinfo. So, your input is appreciated.

CurtP

What's sketchy? The EPA is very clear about hydrocarbon refrigerant replacements - they're illegal to use for anything other than industrial process refrigeration. http://www.epa.gov/ozone/snap/refrigerants/hc-12a.html
No hydrocarbon refrigerant manufacturer has stepped up to the plate to address the safety issue with the EPA, even though the EPA has openly said they will review any additional data they receive.


At the bottom of this page is a list of common acceptable replacements and what they contain (in %): http://www.epa.gov/ozone/snap/refrig...s/chiller.html

ehall

Look around the net for a while and you too will find all sorts of misinformation, and speculation. The fact that the EPA has the info still doesn't seem to stop all of the crap out there. SO yes, there's a lot of sketchy info.
THE WHOLE PURPOSE OF THIS THREAD is to have real info in one spot.
What part of that do you find confusing?

VanhireBoys

Gents
My 951 A/C has been empty since I got it in Sept 2000... Am I doing any harm to the compressor and associated bits...?

I intend getting a conversion kit and seeing if it still operates... We dont need it here in Donegal in fairness....!