A/C completely rebuilt...R12 or 134????

[richard1]

In the last three months, a friend of mine who is a MB A/C technician has rebuilt my original after market 72 A/C.

It took time because finding a compressor replacement was not easy ( the rotary one ) and everything has been replaced including all hoses.

In the next few weeks, I have to decide if it will run R 12 or R 134a. I have the Honda motor blower that is stronger than the original Nissan. In summer here we are close to 117 F.

He believes that I can go with R134a because I will not see any difference, the system still having rubber hoses that absorb heat no matter I have installed insulation on all of them.

Some savy members here to give me advise?

[280~Master]

Go 134a

Danielson If done right no can defend.

You can get 134a just as cold as R-12. R-12 is a thing of the past and is harder to get to every day. Most of the R-12 is recycled and will not be up to par at 117. Steve Blake might give some better advice on the subject.

[sblake01]

I am afraid of the higher pressures that R134a requires to run efficiently in the older systems. My recommendation would be Johnsen's Freeze 12. That's what I use in the R12 systems I have and I've had no problems. Have your buddy check it out. You can read about it here: http://www.freeze12.com/. The best place I've found price wise for 30 lbs. is here: http://store.lenzdist.com/product.php?xProd=722&xSec=1 or in 12oz. cans: http://store.lenzdist.com/product.php?xProd=1045&xSec=4

[Z train]

134a is inferior to R-12 in every single measurable way.

[hls30.com]

Except when it comes to leaving OZone alone, and time required in getting certified...

Will

[Z train]

Except when it comes to leaving OZone alone, and time required in getting certified...

Will

R-12s"effects" on the ozone are THEORY-no proof what-so-ever.

No side effects.

COMPLETELY harmless.

Now lets look at R-134A:

PROVEN corrosive

PROVEN carcinogen

And proven inferior in retro-fits.

Here's a poser for you all:Who took R-12 off the market?

[DatsunZGuy]

Albeit not my 240Z, I swapped out the R-12 on my 1993 MR2 to Freeze 12 about a year ago. No problems with the switch and I am very satisfied.

[Carl Beck]

Hi richard1:

First Answer:

R12 or R134-A really considered by themselves do not matter. Both have to be considered in the overall context of the specific system involved.

Compressing a gas at one point, letting it expand and absorb heat at another point, then dissipating that heat at still another.... involves several different components in different ways.

Because the molecular size of R12 is larger than that of R-134a each gas requires different design components to be used in the A/C System. For the sake of efficiency, in picking up and dissipating heat... the gas molecules have to be keep in close contact with the metal tubes in the evaporator and condenser. While the difference in molecular size of the two may seem very small...compressed and moving at high speed though the system, the very small differences compound to produce very large differences in results.

So systems designed to run 134a have smaller diameter tubes and more of them, than systems designed to use R12. You can run 134a in an R12 system, but you will lose about 20% of the efficiency of the system - -- You can make some of that loss back up, by running higher pressures, moving the gas faster and conducting more air flow over the condenser and evaporator... but at the same time, you'll most likely be trading off system reliability and longevity. Plus having to install larger and/or more powerful fans etc.

The rubber A/C hoses that used to contain the R12 molecules, will not do as good a job of containing the 134a.. it will slowly seep out, and in so doing, it will slowly degrade the old hoses as well. Systems designed for 134a have higher quality shielded A/C hoses. Likewise the compression fittings in the old R12 system, that were tight/secure enough to contain the R12, will not do as good a job of containing the 134a. Systems designed to use 134a have O-ringed compression fittings for that reason.

Modern A/C systems, that were designed specifically to use 134a are just as effective/efficient as the older R12 systems.

If you plan to keep an old R12 system - and you have rebuilt it with new R12 components to avoid leaks... I'd keep it filled with R12. Yes it is more expensive, but then it doesn't take much to charge a system in the first place, and the old R12 systems held their charge for years and years without a problem.

On the other hand, if you are going to install a new system - make sure it was specifically designed for 134a. Aftermarket manufactures, and indeed A/C supply places will tell you either gas can be used in their systems. So many years after the change over to 134a, most of the newer system components have indeed been redesigned for 134a... but you still have to be careful when you buy... and yes quality components are more expensive in the 134a systems.

The newer compressors (rotary type/style) can be used with either gas, as they all have o-ringed fittings in the first place, and the compressors are fully sealed to contain the necessary pressures.

FWIW,

Carl B.

[Carl Beck]

Second Answer;;

A/C in a 240-Z

The 240-Z is a VERY HARD car to air condition. The three major problems I see/encounter are:

1. The Car Is A Greenhouse - huge glass area

2. Very poor air circulation though the long narrow cabin area. The seats and passengers block any real circulation of cool air, though the area with the greatest amount of heat - the rear luggage area. So at best you have only a small amount of cool air blowing in your face.. but no air circulating around your entire body, nor cooling the hottest areas of the cabin.

3. Air leaks...and an all but nonexistence of insulation between the metal body and the interior. In most places there is only a thin "dead air" layer for insulation.

All this means that in very hot area's of the US - the original Dealer Installed, aftermarket A/C units are all but worthless. They certainly will NOT cool a hot car interior down, in less than several hours of driving. If you park the car in the shade, start out in the cool of the morning, you might keep the interior cool enough to live - but not when you have 115 degree heat driven by the bright sun beating down on the car (for that matter anything above 90 degrees is too much to overcome with these old systems).

The Factory Air in the 280Z's was far better - partly because the 280Z's had better sealing cabins, more heat/sound insulation and far better designed A/C systems to work with. Even then, by todays standards for automotive A/C.. they really aren't what you would expect of a modern A/C system in any car.

I used a unit from Vintage Air... a single,self contained combination heater core, A/C evaporator coils and blower motor all in one box (Super Cooler III). It puts out huge volumes of cold air compared to the old dealer installed add on units - and the Vintage Air system will keep the car cool when driving on the road... the problem is, it also dumps huge volumes of hot air from the condenser, directly in front of the radiator... A radiator in the 240-Z that was never intended to support an A/C car in stop and go traffic, in very warm area's.

With enough time and money - most of these problems could be overcome... On thing that would help a lot would be a rear evaporator/blower/fan. Something that would get the air circulating though the entire cabin. Or a duct under the center console, that would deliver cool air to the rear cabin area.. The air flow coming out the vents in the dash - gets sucked back into the system under the dash on the passenger's side - so circulation is very limited indeed.

Heavy Tinting on all windows helps..

New Seals in the doors, windows, rear deck lid all with proper adjustments - helps

Additional insulation in the doors and rear quarters.. helps

but so far - nothing adds up to A/C as good as you will find in any modern car....

FWIW, ..... living in Florida...

Carl B.

[richard1]

Carl, I really appreciate your long posts with all this information. Your suggestion is pretty much the same as my friend told me: don't expect miracles.

Quite frankly, for all these years, the A/C has been fine but certainly no to our modern standard.

I don't expect it to be better but at least operational and giving some " fresh cold air " during the hot days.

There is one subject I would like to explore further from your comment.

If the R 12 molecules are larger, you explained that it is more appropriate for a rubber hose system. Am I right?

If so, I believe that I am better to stay with R 12.

Furthermore, the compressor is the exact same as the original as the new evaporator and " valve " ( my apology to miss the right part description ).

The " radiator " ( sorry again ) in front is the same and has not been replaced and is the only part not removed in this refurbishing of this A/C system. Again , all hoses are new.

I still believe that my best option is still R 12. Do you agree?

[bigoak]

This thread almost makes me happy I drive my Z in Canada...

oh...wait...

BTW...Unbelievable detail Carl. An education on A/C.

Thanks!

[280~Master]

Carl,

All I can say is WOW and how right you are about the rubber hoses, the Z cars air flow, The Greenhouse effect in a Z and how O ring fittings would be better for us.

I have a 76 280Z that now has factory AC (Copper lines) vs. Dealer installed AC (Rubber Hoses) with 134a in it. (I do have the JTR radiator and a Ford Taurus electric fan with an L28 not a V8, more on that later, which causes the car to run much much cooler) but when switching to factory installed AC, I looked into placing 134a low and high pressure valves inline just like newer cars and found out that the copper lines are the same size or close enough to the newer cars that there should not be a difference.

The newer ones are just made of aluminum. If I had a 240Z I would try and find a 280Z with factory and dealer installed AC and modify it to work in a 240. I know there is a difference in the controls but it can be done if you use both dealer and factory setups.