90C2_Cab

The A/C in my car is totally worthless and needs some attention and possibly repair, but, I wanted to ask if anyone has experience retrofitting their 964's using R-12 to HC-12a? Reclamation equipment can be had for cheap($250-$500) and the HC-12a does not require a license to handle. Making it a feasable DIY.

Cheers!

--Eric

springer3

I am not sure if it is still posted, but when I needed information on R12 replacements, the EPA web site (www.epa.gov) had a complete list, good technical information, and pros/cons of the various alternatives. It is a little depressing, because R12 is a pretty good refrigerant for car systems. There simply is no replacement as good for cooling and long life.

Most "drop in" R12 replacements are mixtures of light and heavy refrigerants designed to have the same properties of R12. The problem is that everything leaks a little, and the light refrigerant leaks out much faster than the heavy one. The mixture in the system gradually shifts to higher concentrations of the heavier gas. Topping up helps, but over time your performance deteriorates significantly. R134a is the better choice. It is not a mixture, and so will have consistent properties. Performance degrades only 2 - 3% - not enough to notice unless the system is marginal.

R134a conversion does require new hoses and removal of all the oil from the system, but that is a good idea for any system as old as even the newest 964s.

90C2_Cab

That's what I thought, but, it looks like the 134a is actually the least efficient and most hazardous refrigerant out there. It turns out Du Pont wanted to maintain the monopoly on refrigerants(R-12 R22) by introducing 134a to the market. Many companies are using the HC-12a and forgetting about 134a altogether. The EPA is not independent in its decision making ($$$$). read this.

http://www.oztechnologyinc.com/index.htm

http://www.autocool-refrigerants.com/

--Eric

springer3

Oh please! If R134a is such a fraud, why does every car maker in the world use it? Because it is the best available alternative to R12.

The R12 drop-in replacements are a stop gap. Durability and performance are not nearly as good as a well sorted out R134a conversion.

What do I use? R12 in my 86 Mercedes 300E and 92 C2. R134a factory charge in my 2000 Honda and 2000 VW new beetle. All work fine over many years.

john thompson

A/C is quite necessary down here is S.Texas. I simply bought the replacement valves for the compressor (1991 c4 Cab)....refilled the system with R-134 and for a year all has worked very well. The system was already empty due to slow leak somewhere. I do have to top it off from time to time as cooling drops...but this is very easy and very cheap until I can start replacing parts.....I know you read all about the harm mixing can do...but my system was shot...not working and I wanted a cheap fix. So far everything works great.

John
Texas

JW in Texas

I've got a slow leak in the '90. I have been recharging in May with Freeze 12 for the last 3 years with no problems. Cools very similar to R12 & I have had no issues. Takes about 3 cans once a year ($ 20.00 ttl.).

911kid

I just had my condenser and pressure switch replaced because they were leaking. The mechanic recommended F12 or Freeze 12 as a replacement for the R12. Says he has had good luck with it. Totally compatable with R12 oil. Cost is about $50 for four cans required to charge system.

Jeremy Cottrell

Dennis do you notice a bid difference between the R12 and the Freeze 12?

911kid

Jeremy,

I find the Freeze 12 very comparable in temperature to the R-12. I get 50 degF out of my center vents with either refrigerant.
From information available on the internet I found that Freeze 12 is a blended refrigerant and contains 20% HCFC-142b and 80% HFC-134a.
So far I am satisfied with the replacement.

springer3

The expansion valve controls on freon temperature at the exit from the evaporator. It therefore makes perfect sense that a properly charged system at low to moderate cooling loads will have the same air temperature regardless of refrigerant. I'll bet you will see differences in the system pressure and the load on the engine.

The difference between R12 and R134a is in the range of 3 - 4% in maximum cooling performance with all other factors equal. This is not detectable by the "air in the face test". Compressor performance, cleanliness of the heat exchangers, and charge level make a greater difference than 3% - 4%.

R134a conversion requires "barrier hoses" and oil changeout. Freeze-12 is designed as a "drop-in" replacement for R-12, and supposedly does not require barrier hoses and oil change. However, Freeze 12 is a blend, and has disadvantages relative to R134a. I have heard several stories of people that used R134a to replace R-12, and had no problems. Considering the cost for a conversion, it seems reasonable to run with anything that works until the system needs repair. R134a is the best available alternative to R-12. I am not aware of anything coming on the market to challenge that position. When my R-12 finally leaks out, I will do the R134a conversion.

911kid

What are the disadvantages you referred to concerning the Freeze 12 and the R-134a? Also I've heard it said that the replacement of the R-12 hoses with ones with a barrier liner are not always necessary since the oil tends to permeate the hose after 15 years of operation and blocks or slows down any leakage of the smaller R-134a molecule. Have you heard of this?

springer3

My earlier post talked a little about the disadvantage. A blend of refrigerants in a system with any leakage will quickly contain mostly the heavy part of the blend. Performance will suffer, and you will over-work the compressor. See my recent post on my AC belt if you want to see what can happen when the head pressure gets too high. I suspect I lost my condenser fan, and the high head pressure caused or contributed to the destruction of the AC drive belt.

I agree the difference between barrier hose and non-barrier is probably small. Barrier hose has been standard since the mid 1990s. If you have non-barrier hose, it is probably 10 + years old, and overdue to cause problems anyway.

90C2_Cab

I decided to try the Envirosafe HC-12a hydrocarbon refrigerant "drop-in" instead of HFC-134a and have had great results. It took two cans valued at $7.50 each and I didn't have to use it all. The A/C now blows COLD. This refrigerant is a mix of Propane,Butane and isobutane. This does not exactly classify as a blend, since they are all HC's with relatively similar molecule size, and dont have the tendency to imbalance as the blends do having different molecules leaking at a different rate. As you can see the blends are a mixture of several different gasses and contain some global warming(R134a) and even ozone depleting(R22) gas

Free Zone (RB-276). Supplied by Refrigerant Gases, this blend contains 79% R-134a, 19% HCFC-142b and 2% lubricant.

Freeze 12. Supplied by Technical Chemical, this blend contains 80% R-134a and 20% HCFC-142b.

FRIGC (FR-12). Made by Intermagnetics General and marketed by Pennzoil, this blend contains 59% R-134a, 39% HCFC-124 and 2% butane.

GHG-X4 (Autofrost & McCool Chill-It). This blend is supplied by Peoples Welding Supply and contains 51% R-22, 28.5% HCFC-124, 16.5% HCFC-142b and 4% isobutane (R-600a).

GHG-HP. Also supplied by Peoples Welding Supply, this blend contains 65% R-22, 31% HCFC-142b and 4% isobutane (R-600a).

Hot Shot\Kar Kool. Supplied by ICOR, this blend contains 50% R-22, 39% HCFC-124, 9.5% HCFC-142b and 1.5% isobutane (R-600a).

The hydrocarbons(OZ-12, Duracool, Autocool, Envirosafe etc..) on the other hand are lighter(require less hp to turn compressor) NON global warming and NON ozone depleting (R134a is a global warming component). There is no problem using HC-12a in a system containing air or moisture, and no oxidation problems, it is miscible with both PAG,POE or ester type lubricants AND mineral oil used in R12 systems(R134a and mineral oils will not mix therefore, starving the compressor for oil and causing failure). It also has the lowest cooling temperature of R12 or R134a.

The "legal" issues surround doing an "approved" retrofit which requires converting an R12 to R134a system before using a hydrocarbon refrigerant, not the flammability issues which are truly nil.

check out http://autorefrigerants.com/ for someadditional info.

--Eric

springer3

A little dose of snake oil would work well as the lubricant for some of these mixes. There is a reason the car makers use R134a exclusively. Name one that does not.

Randall G.

The 964's system was designed with R-134a in mind--Porsche knew the new gas was just around the corner. In essence, it's a R-134a system. Thus, when converting to R-134a, all you have to do is evacuate the old R-12 and its oil, replace the receiver/drier & high/low ports, and you're set.

R-134a was introduced with the '93 964. Haven't heard of any '93 964 owners complaining of their A/C being inferior to earlier 964s.

If you convert your pre-93 964 to R-134a, you use the same quantity of gas/oil as the 93+ cars. In fact, the quantity of gas/oil (840g R-134a, 140 c.c. ND8 oil) is the same as it is for the 993. Pulling the thread further, the center vent/pressure graphs for the 993 and R-134a 964 are exactly the same.

If you study Porsche's center-vent vs. ambient temperature graphs, R-134a actually out-performs R-12. At least up to 40C, where the upper-band of the R-134a curve isn't shown.

My point? A pre-93 964's A/C converted to R-134a can perform as well as the A/C in a 1998 993. As it does for my own converted car. Despite all the bashing R-134a gets. The only advantage I can see to drop-ins is to avoid having to purge the old gas and change out the receiver/drier.