Quantity of R-134A in up-graded A/C in 88/911

[Vince Cappelletti]

Hi Guys, Gals,
Seeking inputs from those of you who are familiar with the A/C system in the 911 Carreras, in particular, the '88, and hopefully someone who has also up-graded their system. Here's the situation.
Two years ago, I did an up-grade to my '88/Cab A/C system. I retained two components that were in the system when I purchased the car: The rear Condenser, and the NipponDenso Compressor.

I went to Rennaire out in Tx. and purchased their: Desert Duty Front Condenser which is basically double the thickness of the original unit provided by Porsche; their Pro-Cooler [dryer-bottle] which is also somewhat larger than that in the original system, and their Serpentine Evaporative cooler, which also, [supposedly] contains more cooling coils & surfaces. I also purchased a complete set of Rennaire Hoses.

At the rear condenser I added a DeRale Sucker fan that moves some 500 cu.ft./min when I turn on the A/C Compresser. This blows in conjunction with the Front Condenser Fan. At the Evaporator I added a Griffin Fan-Motor that moves a lot more air than the stock motor. In the cockpit I added the Kuehl Evaporator Fan Variable Speed Controller. [also by Griffin] All have worked well for two years until recently when I noticed the A/C was not as cool as it had been. I took it to a local Shop I know quite well, and I was informed that the output valve was finger-tight and had leaked out most if not all of the R-134A. Now here is where it gets iffy: the shop added 33-oz of R-134A, and I witnessed a wire probe reading of 48-degrees "F" in the left dash vent, at a low fan speed.

It was my understanding that the original system was loaded with 47.8 oz. of R-112
Refrigerant, [so indicated on a decal] and: when one replaces the R-112 with R-134A, you introduce a lesser amount due to the different chemical structures of the two gasses. The "wrench" yesterday indicated that you use only 80% of what was used when R-112 was the refrigerant.

Well, 80% of 47.8 oz. comes to 38.08 Oz. Telling me that perhaps not enough R-134 was added.

As a result today, when I drove the car in 80-degree ambient temp, I could not get the Temperature @ a dash-vent to read lower than 60-degrees "F".

Add to that, I was also informed by yet another "wrench" that when replacing R-112 with R-134 one would reduce the amount of "charge" and only introduce 70% of R-112 coolant.
So there are a couple of questions I need answers too!
1. Which is correct, 70% or 80% or is it something else?
2. As a result of adding components to the system that are larger in volume, should not the amount of coolant be increased as well? OR? does it matter??

I've written to Rennaire and inquired about the increased volume of their Front Condenser, Pro-Cooler, and their Serpentine Evaporator, and have yet to receive a response.

Has anyone gone through this sort of upgrade? and encountered similar issues?
I'm due back there tomorrow right after lunch for another look-see.
My next thought is, I might have a loose hose-connection.
All comments welcome.
Many thanks,
Old Rakasan
Bonita Springs, FL.

[wwest]

The simplest way is to buy one of those inexpensive R-134a charge kits that includes a low side pressure guage, a few cans of DuPont branded R-134a, and follow the instructions approved by DuPont.

[Vince Cappelletti]

Thanks, Westy,
I have one of those cans.
Old Rakasan

[Arne2]

When mine was done, the A/C shop used 30 oz. of R134a. I don't have the procooler, but the rest of my system is pretty much the same. Works reasonably well.

[Vince Cappelletti]

Hi Arne,
No, the thought of a Nissan or Mitsubishi never entered my mind. I started out driving 356's with a '56 Coupe back in 1957. I bought it off a BOP Dealer's lot in Tulsa. At the time I believe there were 6-356 Porsches registered in Oklahoma, mine became the 7th and I had a Factory work-shop Manual. I've never looked back. Later in life, I had a "Barn-Find" in Tremelo, Belgium, in 1982. It was a 58-1600 Speedster, VIN-84437. if you were to look up the D'Ieteren Collection in Belgium, you will find it there. Roland has it as part of the D'Ieteren Rally Team. Dr. Michel Thiriar who wrote the 1st Speedster Book was the 1st owner [actually he was the 2nd as it was purchased by his Grandfather] as Michel was only 17 at the time and not old enough to own a car, I was the #10. Michel mentions me on the bottom of Page 118 as the one who restored it and sold it to Roland D'Ieteren for their Collection. The car appears in several photos driven by Roland or Phillip Casse, the PR guy for the D'Ieteren organization.
I toured it throughout Europe for a few years and then sold it to Roland D'Ieteren and it entered the D'Ieteren collection in the spring of '88. I turned my attention to other 356's & 912's, and 911's and even ran a 2.0L Cosworth Turbo-Engined Ford Sierra for awhile. There was a 60/B Coupe, a 65/SC w/SR and a '68-Soft-Window Targa, and a '62-911SC. Upon my retirement at the end of '96 I returned to the states and SW Florida and through friends and colleagues in the 356-Registry ended up with #161990, which is a '65/C Cabriolet that had undergone a Stoddard bare-metal restoration. I had it shipped here and drove it until April of 2011 and in the process put some 150,000+ miles on it. It now is stored away in a dry warehouse down in Naples, the property of a young man that had always lusted after a 356. So, I've really never fancied a Nissan, or a Mistsuibishi, but In those interim years I admit I strayed from time to time, as I turned the key on some other cars, there was a: '58 Corvette; '59 Alfa Spyder Veloce; a VW; a MG-TD; an Aluminum bodied Maserati AGC6 Coupe by Zagato; and later a Maserati-3500GT with a Touring body, that I drove around Italy on "Provo" plates before shipping back to California where I was living at the time. Then there was a lovely 300SL-Gullwing that I had after parting with the 3500-Maser-GT. In fact I keep track of that one and know where it resides. There was a Maroon '49-Cisitalia Coupe that marked me to the SD police as a "speeder" when in reality it was not the speed it was capable of, but the noise and smoke it emitted when crossing Kearney Mesa between Plant #2 and the former "Astronautics" Plant on HW-395. When I sold #161990, I moved on to the '88/911 Cabriolet as there comes a time when you just can't ask the Missus to get out one more time and give me a little shove in reverse while I pop the clutch, because the 356-starter is acting up again. The drives to East & West coast Holidays of the 356-Registry, were always a challenge, as much as the drives to the European Reunions, and European Parades
every year a different country. No, All I'm currently trying to do is get the A/C working again on the 911 as it did on the drive out to Santa Fe in the fall of '13 to the WCH of the 356 Registry. The missus never had to push me once, and the working A/C made the drive a pleasure.
Thanks for the comment,
Old Rakasan
Bonita Springs, FL.

[kuehl]

pm sent

[DaveMcKenz]

I think Westy is just playing games with you. It will never be as simple as what he said. He will soon expound.
Good luck,
Dave