Koenig928

The size and heat transfer capability of evaporator /condenser in the S4 is really designed for R12. R134 will work, but not that great. R134 operates at a higher temperature and pressure, and I've found the hotter is gets outside, the less efficient it seems to become inside the car (summers here in Vegas are brutal). Also, the R134 molecule is smaller than R12, and will tend to leak throught the rubber sections of a/c line, but it will work.

I'm currently converting both of my cars back to R12 from 134.

R12 is still for sale on the market and I've found Ebay is the most economial way to buy it, expect to pay ~ $20 - $25 for 'old stock' 12-14oz cans. (Although, NAPA auto parts still sells it for $47 per 12oz can).

If you don't have an EPA 609 Certification card, you can easily get it at www.epatest.com for $19.95. It took me ~1.5 hrs to do mine.

Tom in Austin

I converted a Nissan years ago and it was nowhere near as good as with R12, especially sitting stopped and idling ... as we so often do in Austin :-(

If I had an R12 car I'd make sure the system was tight and keep it R12 ...

vsalvato

Guys, can someone tell me what is the rough estimate cost for retrofitting an R12 A/C to R134 on an S4/MY88? IS the retrofit going to reduce in any way the life expectancy of the A/C system? Thanks

ShawnSmith

I like to think of my 928 as being a fancy rolling storage facility, keeping several liters of R12 from escaping into the atmosphere. If we can find a way to wrap a 928 around some spent reactor material (and use it to go really fast) I'd like that too

howdog928

This is very good to know Bill. Right now in looking at the whole R12/R134 issue, converting to R134 seems to be an expensive undertaking if done right to change out everything needed. So the main problem I now see is how can I buy the R12 I will need. If I can buy it, I can get my A/C sorted pretty cheaply.

griffiths

Roughly $100.00 in parts, plus anywhere from $100 to 200 refrigerant and labor.
However, if you are considering converting then you probably have leaks somewhere (typically compressor, hoses at compressor or expansion valves or their o-rings). So there would be additional labor and parts whether you are converting to R134a or trying to repair an R12 system.

I've owned 3 Sharks with and without rear air. Converted them all to R134a and they all cooled just as well as R12 right up through the high 90's F .
Many dissatisfied conversions can be related to other issues, such as continual leaks not repaired, fresh air or mixing vent problems, improper evacuation and charge. The stock 928 condenser and evaporator do quite well with R134a.

Koenig928

Ebay is the easiest way to buy it without a 609 card. They make sellers list a disclaimer - something like "by bidding on this item, you're verifying that you have an EPA 609 Certification, or are going to resell this item to a 609 certified technician". It's totally up to the seller to check this. 2 of the 3 sellers I bought R12 from did not even ask for it.

But a word of caution, I would recommed staying with the individual sealed cans. Steer clear of the 30lb cylinders, unless you know the seller.

Good luck.

howdog928

Hi Griffiths,

When you converted yours over to R134, what exactly did you get changed over?
I've read somewhere before here on RL that the R12 system is not set up for the 134 higher pressures &is needing fan changes or something.

Still trying to wade through all the opinions on R134 or R12.

dprantl

There's a lot of BS around the R12/R134a topic. Here are the facts:

- R12 is more efficient than R134a. It will yield colder vent temperatures at lower high-side pressures
- R12 is much more expensive than R134a and is more difficult to acquire
- The 928 has a very large condenser in comparison to its interior volume when compared to most other cars
- When converted properly in a healthy system, R134a will be able to cool more than well enough up to 100 deg F humid ambient temps in a black 928
- To convert to R134a properly, at a minimum you really need to change all the o-rings in the system, the drier, the expansion valve(s), and also flush the lines, evaporator(s) and condenser and drain the compressor of all the mineral oil. Then you need to add the correct amount of ester oil, then add the correct amount of R134a
- It is questionable how long a compressor shaft seal designed for R12 will last in a R134a system due to the higher system pressures. In order to be sure the system lasts for years without leaking, you need to replace the rubber A/C hoses and get a compressor with a shaft seal designed for R134a
- A modern aftermarket parallel-flow condenser designed for R134a is available for the 928 for <$200. This helps to keep R134a system pressures lower

Everyone can derive their own conclusions from these facts.

Dan
'91 928GT S/C 475hp/460lb.ft

Ed Scherer

I've gotten R12 both off eBay (and confirmed eligibility to purchase by sending a link to an image of my EPA Section 609 certification card) and at NAPA. The NAPA stuff was in nice, new cans, probably manufacturered in Mexico; eBay stuff is usually old—sometimes very old stuff—but it probably doesn't matter.

Yup, ditto all that. epatest.com is Mainstream Engineering; that's also where I got mine, and I can also recommend them.

IMHO, cost of refrigerant is the only reason to choose R134a over R12. Make sure you've got a tight system (i.e., no leaks) and, yeah, you'd pay more for the R12, but that just doesn't seem that significant to me compared to all the other considerations.

Dan's comments are on target, too, IMHO.

One final thought: avoid weird blends and strange refrigerants that aren't R134a or R12. Their main disadvantages: some (but not all) are highly flammable, and you might have problems finding anyone else willing to work on a system with such refrigerants. Actually, I suppose that's another advantage of R134a over R12: it's the refrigerant that you can be pretty sure any A/C shop is happy to work with.

griffiths

On the past Sharks I owned:

1978 - initially using the stock 78-79 boat-anchor compressor: did a simple conversion by recovering the R12, replaced drier and it's o-rings, attached R134a charge port adapters, pulled a vacuum, injected 8 ounces of ester oil, charged with R134a based on a Temps and Pressures chart. Performance up through the mid 90's (not a hot summer) was just like an R12 system. Later, when we developed the Kuehl compressor kit, we recovered the R134a, replaced the 2 hoses at the compressor with our barrier hoses with new o-rings, evac'd and charged with R134a like before. Ran this set up for about 4 years and performance was like a stock R12 system. Then sold the car because we started a family and "wanted" an mini van.

1984s - initially using the stock 80-89 compressor: ditto above on a simple R134a conversion. Then again tossed on our Kuehl compressor. Same results, very good performance. Then sold the car because the 'x' wanted a house.

1989s4- stock compressor was worn. Installed the Kuehl Compressor kit, had to replace leaky expansion valve for front evaporator, hoses, drier, did R134a conversion. Performance excellent however never really needed to run the rear ac because its useless other than to keep a lobster chilled between the fish store and the grill or a six pack of becks for golf course. God.. I loved that car..... But, trying to be a good guy... had to sell it to buy new kitchen cabinets for the money pit. And, learned a valuable lesson... don't sell the car,
rather sell the blank instead, lol.

In the mean time I'm air cooled, 87 911 cabriolet with every conceivable ac product installed including a blower (hp and torque undisclosed),,,, waiting for the Perfect Shark to come along again.

howdog928

Awesome info, thanks.
Can you tell me a bit more about the parallel-flow condenser please. Is this an add-on to the system?

griffiths

There are several condenser designs:
single row tube and fin
2 row tube and fin
3 row tube and fin
small diameter tube and fin
piccolo
serpentine
parallel flow
plate and fin
and then you have other terms related to design, some terms
depend upon the mfg's unique description such as 'micro channel',
and then there is the the width of the coil in terms distance front to back
sometimes referred to as thickness such as 16mm, 22mm, 25mm, 44mm,
and number of channels in the tube, the shape of the channels, and then there are styles of shapes of the cooling fins between the coils and the number of fins per linear inch.

Early sharks had serpentine coils, then they reverted back to the earlier tube and fin
design.

Present OEM vehicles tend to have parallel flow micro channel which to dump more
btu's however they are more fragile and more prone to leakage.

I found in my conversions to R134a using the stock condenser in the car worked quite
well and most issues in terms of the condenser being suspect to not working well ended
up to be a fan issue or a shroud not in place (hot air recirculating back into the coil). More common problems or disappointments with R134a conversions relate to poor evacuation, air in the system, over charging, not charging by pressures and temperatures, or something like a fresh air flap solenoid, blend doors not closed, heater valve open.

If it come time to replace a coil you might want to consider serpentine or parallel flow,
it all depends upon the mfg's design, such as number of coils, distance between the coils,
cooling fins per inch, thickness of the coil.

When you get into very hot climates, ie. 100F or leaving your shark to get
radiant heat soak in the sun outside you may find driving with the windows down and ac off for 5 mins is more effective since the cockpit is 130F and the outside air is 100F that gets you back to 100F quicker than the ac will, and then turn on the ac and up the windows.

If you have an engine running hot or radiator not doing is job, or something blocking air flow to the condenser such as an intercooler for your supercharger then naturally you will lose condenser performance.

On extreme hot days a condenser dumps heat into the radiator and visa versa.

blown 87

There is a reason that none of the pros here that I am aware of will do a 134a conversion.
I sure wont do one anymore.

griffiths

What problems did you encounter when converting ?