R-12 or R-134 in '88 A/C System

[Vince Cappelletti]

Hi Guys,
I'm in need of your collected wisdom. I've recently acquired an '88-911 with A/C.
When I purchased it, I was informed that it had already been up-graded to the new R-134.
When I took it to my favorite wrench to sort out a few "pimples" it was noted that the A/C system was completely empty of Coolant, and required a complete recharge.
Later I was chatting with a pretty knowledgeable 911/Parts guy, and he made mention that the so-called up-graded R-134 does not cool as effeciently in the "Older" A/C Systems as the R-12. He strongly suggested I have the R-134 Flushed out, and have the system re-charged with the older R-12, AND at the same time, Change out the Dryer bottle that is located in the rear face of the left Wheel Well.
I really would like to have an A/C system that works as now that it has been recharged I find that I have a ceiling fan out in the garage that provides more cooling than this A/C System, unless I'm driving @ speed on the Interstate. Living down here in SW Florida I could use an A/C System that provides some relief
Could I have your thoughts on this?
Thanks for listening.
Vince Cappelletti
Bonita Springs, FL.

[mnmasotto]

There are lots of posts on the A/C system in your car on this forum. Read them and you will learn alot about the limitations of your 25 year old system. In a nut shell, your system, asuming it is stock, probably has developed quit a few leaks. I suspect simply filling it with R12 will not last long. I have have spent over $8000 on a complete Griffiths A/C System and it still does not work as well as my 2006 BMW. At the very least, you should replace your hoses, evaporator and dryer. Then charge the system with R12. It will cost more than R134 but is definitely more efficient. If you would like to discuss my experiences with my 87 Carrera you can PM me and I will forward my phone number.

[Barrpete]

The answer is - it depends. What were the upgrades? There's a slippery slope here with simply changing the reciever dryer, compressor valves and adding R134A ($'s) on one end to upgrading condensors & evaporators, adding condensors, adding fans, switching to barrier hoses, etc, etc. etc ($$$$'s).

Even with the most expensive upgrades if there's a leak in the system it doesn't matter what refrigerant you use it won't work once the refrigerant is gone.

My advice is figure out exactly what your system is first, and what condition it's in. If it's a stock system that someone just swapped out to 134A it probably is only going to be marginal at best. If it's stock - and in good shape - going back to R12 might be the least expensive way to go. If components are bad it may make sense to start from scratch. I replaced my entire system with the Rennaire System II running 134A and get comfortable temps in Tucson summer heat, not as good as my Chevy truck but not bad. Also do a search there's a ton of threads on AC improvements. Here's a good place to start:

Ultimate AC Thread

[vracer]

There must be about 100 auto a/c shops within two miles of your home in Florida. Find one that has someone there who has been working of these air breathers for the last 15-20 years. But FIRST spend a couple or five hours reading various threads so you will have some idea if he knows what he is talking about.

[RSTarga]

Originally Posted by mnmasotto

There are lots of posts on the A/C system in your car on this forum. Read them and you will learn alot about the limitations of your 25 year old system. In a nut shell, your system, asuming it is stock, probably has developed quit a few leaks. I suspect simply filling it with R12 will not last long. I have have spent over $8000 on a complete Griffiths A/C System and it still does not work as well as my 2006 BMW. At the very least, you should replace your hoses, evaporator and dryer. Then charge the system with R12. It will cost more than R134 but is definitely more efficient. If you would like to discuss my experiences with my 87 Carrera you can PM me and I will forward my phone number.

How about telling us how you spent 8 grand on griffiths system.

[Vince Cappelletti]

Mr. Masotto,
Thanks for your comments. Yes, I would like to chat with you about your efforts on your '87. I don't think I can afford to spend $8K on improving the existing System, but I'd like to at least understand it's limitations, and its weaknesses (that's a plural!) I can be reached @ vincecappelletti@embarqmail.com, and my home phone is: 239-498-6461. I've got a cell but with 2-hearing aids, I seldom hear it, even if it is on vibrate. With kind regards,
Vince Cappelletti

[Vince Cappelletti]

Hi Richard, Yes, you're right, I've got to do some homework here, read the posts on A/C issues that have already been posted, and then talk to some knowledgeable guys in the business. Most local shops are not "Experts" in the field. They're great @ working on the major componets of the car, but when it comes to A/C, it's a whole new ball-game. Thanks for your suggestion. Regards, Vince Cappelletti, Bonita Springs, FL.

[scottb]

Originally Posted by mnmasotto

I have have spent over $8000 on a complete Griffiths A/C System and it still does not work as well as my 2006 BMW.

How, or on what, did you spend $8,000 for your air conditioner??

[Vince Cappelletti]

Thanks Mr. Barr, That's one of the issues. Knowing just what the so-called improvements really are. I'm inclined to believe, [absent of any other information] in the service records that came with the car that all that was done was a flush out of the R-12, and a re-charge with R-134. I've got some homework to do reading all the data that has been submitted on improvements that have been accomplished by others. Once I've digested that, I'll start talking with some of the local A/C firms, to see what, if any experience thery have had working on 911's. There are a lot of newer cars down here in SW Florida, I'll just have to dig a little deepter. Thanks again for your comments. By the way do you have any kin here in SW Florida as good friends of mine [Family Name of BARR] have a great Restoration shop in Nearby Naples. They specialize in American Muscle cars. With kind regards,\Vince Cappelletti,
Bonita Springs, FL.

[kramer747]

134A and R12 cool just the same. Same with R410A and R22

[wwest]

Assuming the system is properly charged using an R-134 charging procedure, NOT the R-12 procedure, R-134 will work just as well as R-12. My '88 Carrera was converted 2 years ago for less than $200.

The factory A/C system in the air-cooled cars has a MAJOR design flaw, maybe 2 actually.

The pressure downstream of the compressor is limited ONLY by the compressor capability itself(***). The compressor does NOT cycle off due to rising refrigerant pressure as do most newer systems today. The compressor cycles off if, ONLY if, the evaporator surface area, localized airflow, declines to the setpoint you select via the capillary sensor system. That means that on a hot day "start-up" of the system the refrigerant line pressure will be rather extraordinary before the recirculating airflow temperature drops enough to open the capillary sensor system switch.

That's the most likely reason these systems will not hold refrigernat charge from one year to the next.

So...

Have someone install a hi/lo refrigernat pressure limiting sensor switch. The low side detection switch will prevent the compressor from running, and being damaged, with the refrigernat charge too low. The high side switch will prevent the compressor from producing refrigerant pressures too high for the system.

If you then find that the A/C cooling capability is inadequate then add 2 thin 12 volt radiator cooling fans to force more airflow, CONSTANT airflow, through the rear deck condensor. Mine are wired such that both have 12 volts when the compressor is actually running, but only 6 volts, series connection, when the A/C is on but the compressor not running at the moment.

*** And...

Porsche is NOT stupid.

It is entirely possible that the factory original compressor has an internal mechanically implemented high pressure limit. Install an aftermarket compressor without the hi/lo switch for control and you may blow a hose or two.

[Bob Kontak]

Originally Posted by vracer

But FIRST spend a couple or five hours reading

Read enough and you can get yourself an EPA 609 cert, some R12, a set of gauges and maybe a leak detector kit / vacuum pump and some of wwest's parts.

Certification - $25 (plus some study time)
R12 - 20 bucks a can = $60
Gauges - DIY quality - $100
Leak detector kit - $100
Vacuum pump - $175-200 for a lower end Robinair or $15 for a HFT cheap-o version

That would be about what you would be charged to have the expansion valve replaced professionally.

Hire someone to remove the old freon vs buying the $2500 recovery system.

[mnmasotto]

Originally Posted by RSTarga

How about telling us how you spent 8 grand on griffiths system.

Anyone who has sent their car to the local Porsche shop for fabrication work and installation of A/C parts knows the price adds up quickly. I have replaced every part available from Griffiths at least once. In addition, I cycled between R134 and R12. I ended up finding R12 makes lower vent temps. I had my local Porsche shop fabricate a much better fan motor into my blower box (old one made too much noise and did not flow enough air). Although cheaper venders are available I found Griffiths products to be the best quality and best customer service. I also switch from the after market Keuhl compressor to a new factory 993 compressor and clutch at a cost of about $1000. This compresor has a lower profile than the popular aftermarket compressor from the other vendors. In the end, I have a professional installed system with no less than four condensors (one in front, two in the left rear fender and one on the deck lid), upgraded hoses, evaporator, drier, custom fan motor, etc running R12. Again, I works very good but I still like the system in my 2006 M3 or GT3 better.

[Barrpete]

Originally Posted by Vince Cappelletti

By the way do you have any kin here in SW Florida as good friends of mine [Family Name of BARR] have a great Restoration shop in Nearby Naples. They specialize in American Muscle cars. With kind regards,\Vince Cappelletti,
Bonita Springs, FL.

I do, my mother is a snowbird in Fort Pierce, but no relation to the family you know in Naples.

Take your time, evaluate what you have, do your research and decide what will work best for your situation. The AC systems in the Carrera's were really an afterthought, and the weakest link is lack of condensor area to reject the heat. Not to mention that your system is now 23 years old! I would not be surprised if the compressor was leaking around the shaft. Look for a stripe of oil on decklid just above it - that's the telltale sign the compressor needs replaced.

Upgrades that increase condensor surface area and/or efficiency will give the best improvements. Griffith's and Rennaire are probably the best sources of improved AC components. Both offer good quality but I think Griffith's has better hands on support and is more than happy to answer questions. The owner posts here fairly often under the user name Kuehl.

If you decide to upgrade, replacing the AC components is not all that difficult either. It's a bit dirty and tedious but not technically difficult. So you can easily do it yourself and save a bundle of money. And there's plenty of help available here!

[Vince Cappelletti]

Mr. Barr, Thanks for the additional tips. Especially those addressing the condenser itself. I spent considerable time last evening reading some of the many posts regarding A/C in my 23-year-old car, and I think I'm beginning to grasp the the size of the issue before me. I thought I had problems with my 46-year-old 356-Cab! I had hopes that by switching to a younger-model it would be a lot easier. I am beginning to see that is not the case, as the Maintenance-Costs" are going to be higher. I'll certainly be looking @ Griffiths & Rennaire. Regards,
Vince Cappelletti,Bonita springs, FL.