converting from R12

[Davea Lux]

The UN climate agency wants to phase out the use of R134a because it does not break down readily. The current trend is toward non persistent refrigeration gases, mostly hydrocarbons. These oxidize relatively quickly and have no known effects on the ozone layer (neither does R134a). There are also studies being done on compressed CO2 as an alternative to hydrocarbons. Both the hydrocarbons and the CO2 are green house gasses which would seem to run counter to the whole global warming talking points.

Dave

 

[CBODY67]

With 134a, the system is changed to work like a modern system and the compressor is cycled which controls the flow. This is what the T-stat does.

Sorry, but the "modern system" comment made me laugh. No disrespect, BUT back when the cars were new, the less-expensive (aftermarket) systems had cycling compressors while the factory systems (other than Ford) used throttled compressors (whether EPR, VIR, Hot Gas By-pass, or similar) to vary the amount of flow to the compressor so that the evap core didn't become a block of ice. It was also noted that the fuel economy penalty of the constant-running compressor was about 1mpg more than the cycling-compressor systems.

BUT, the A-body Valiants and Darts used a factory cycling-compressor system. All that was needed to make it "Like a Chrysler" was to install an EPR valve in the line to the compressor, in the Chrysler factory location. Reason I know that is that one day, a customer at the local Chrysler dealership had just bought a new Valiant sedan, in about 1974, and didn't like the cycling compressor, so the service dept intalled an EPR valve and unhooked the pressure switch that tuned the compressor on and off.

When those old RV-2, GM A-6, and Ford Tecumseh compressors turned on, it did load the engine, but with a Ford 390 and all of the metal momemtum in that engine, it really didn't affect things like it would in somebody else's engine. The modern Sandens and such don't load the engine that much, by observation, nor the Densos on the '79-'80 Chryslers (which tend to have a more sophisticated cycling system than the 1960s systems did).

In the initial conversions, there was a recommendation to start with about 80% of the R-12 gas charge with the R-134a, then slowly increase the gas charge until cooling performance optimized, which was usually at about the 90% level. Seems that a R-134a system is much more sensitive to overcharge than an R-12 system is.

Also note that the factory R-134a condensers are massive, usually bigger than the radiator on the LH cars, for example. Condenser capacity, the more the better, is an important factor, too. The factory R-134a condensers are "mass flow" rather than "serpentine" (as all of the OEM R-12 condensers are), which can be another side issue. As can be air flow across the condenser at slow speeds in traffic or when parked.

Take care,
CBODY67

 

[saforwardlook]

yes its flammable , its used as a torch fuel . its mainly butane . but gasoline is flammable to right . and carb's vent to the air , the a/c is a closed loop .

It is closed loop until something lets loose.............and then it could become a torch. I know at least vehicle manufacturers worry about that issue.

 

[pomonamissel]

well that has not been an issues , i've even vented it into the shop with out any flaming torches . as a bic lighter it only becomes a flame when enterduced to a open flame or a spark at the right time , can't say i've lite or used a bic to look for leaks under the hood or anything else . it seems you are not including the pressurized gasoline fuel system that is always present , one could state that rubber hoses and questionable fuel lines and routing is always an issue to torch out the running vehicle . and i can say yes to having engine fires due to gas under pressure and the ignition setting it a blaze . not sure if the manufactures are worried about the fuel , every vehicle i've owned or operated has a rubber fuel line joint from the chassi to the pump . but with electric vehicles on the rise , fuel won't be an issue for long . and if people went back to traveling in cover wagons , the fatality rate would drop on the freeways , lol . just like any un-serviced or improper managed vehicle is going to have issues . but the cars we are talking about are mainly garage queens and driven shortly through the year . i'll make my cars services a everyday thing by viewing and listening them for any type issues .

 

[73Coupe]

Sorry, but the "modern system" comment made me laugh. No disrespect, BUT back when the cars were new, the less-expensive (aftermarket) systems had cycling compressors while the factory systems (other than Ford) used throttled compressors (whether EPR, VIR, Hot Gas By-pass, or similar) to vary the amount of flow to the compressor so that the evap core didn't become a block of ice. It was also noted that the fuel economy penalty of the constant-running compressor was about 1mpg more than the cycling-compressor systems.

BUT, the A-body Valiants and Darts used a factory cycling-compressor system. All that was needed to make it "Like a Chrysler" was to install an EPR valve in the line to the compressor, in the Chrysler factory location. Reason I know that is that one day, a customer at the local Chrysler dealership had just bought a new Valiant sedan, in about 1974, and didn't like the cycling compressor, so the service dept intalled an EPR valve and unhooked the pressure switch that tuned the compressor on and off.

When those old RV-2, GM A-6, and Ford Tecumseh compressors turned on, it did load the engine, but with a Ford 390 and all of the metal momemtum in that engine, it really didn't affect things like it would in somebody else's engine. The modern Sandens and such don't load the engine that much, by observation, nor the Densos on the '79-'80 Chryslers (which tend to have a more sophisticated cycling system than the 1960s systems did).

In the initial conversions, there was a recommendation to start with about 80% of the R-12 gas charge with the R-134a, then slowly increase the gas charge until cooling performance optimized, which was usually at about the 90% level. Seems that a R-134a system is much more sensitive to overcharge than an R-12 system is.

Also note that the factory R-134a condensers are massive, usually bigger than the radiator on the LH cars, for example. Condenser capacity, the more the better, is an important factor, too. The factory R-134a condensers are "mass flow" rather than "serpentine" (as all of the OEM R-12 condensers are), which can be another side issue. As can be air flow across the condenser at slow speeds in traffic or when parked.

Take care,
CBODY67

None taken. I didn't know the appropriate term so modern is all that came to mind, haha....

 

[John Kirby]

I looked into finding parts to rebuild a RV2, some parts are available but they are becoming rare. I did find a complete RV2 online but it was over $500, That was 10 years ago. The law of money says nothing ever get cheaper so the Sanden route is what I did. In the process I had to go to billet aluminum brackets since a sanden isn't compatible with RV2 mounting. I went with CVF racing brackets for a 440. I did have to change the power steering pump to a later version. The original pump from '66 is not readily available but the later one is. Here's a photo.

Once all this was installed, a new condenser was ordered along with all the hoses and fittings. A hose crimping tool had to be bought too.

At this point is was install everything. While doing this I replaced all the o-rings in the system with R-134 versions too. An AC gauge set and vacuum pump was borrowed from Autozone to fill the system with oil/R-134. The oil type is stated on a sticker attached to the compressor. There was a copper pipe that went around the back of the engine, I bought an aluminum pipe of the same diameter and had my brother bend it with a tool he uses to install AC systems in houses. An AC shop can do this if you don't have an AC guy around.

I did this back in 2012 and it is still working great. I realize this is more expensive than a RV2 swap. But the RV2's are notorious for working great from the factory until the warranty on your car expires. And R-12 is very hard to come by. It also looks really cool when showing off your vehicle.

The one piece that was critical is the pipe connecting to the evaporator valve. Don't discard this.

 

[Mr onetwo]

Just thought I would add this to the thread.R12 is still around and if you use "Search Tempest" on Craigslist it can be found.There were over 50 ads for R12 all over the USA. Some cheap and some ridiculous. I just received 16 brand new NOS cans of IG-LO Dupont R12 for less than $200 shipped.It can be shipped via UPS legally using the symbol shown in the 2nd photo.Per the UPS hazardous materials dept. Just attach the symbol in a 4 1/2" square format to the box and call the contents auto parts.Went from AZ to ME no problemo. Both my Fury and my Dakota are R12 and I want to keep them that way.

View attachment 489639

 

[Toolmanmike]

Just thought I would add this to the thread.R12 is still around and if you use "Search Tempest" on Craigslist it can be found.There were over 50 ads for R12 all over the USA. Some cheap and some ridiculous. I just received 16 brand new NOS cans of IG-LO Dupont R12 for less than $200 shipped.It can be shipped via UPS legally using the symbol shown in the 2nd photo.Per the UPS hazardous materials dept. Just attach the symbol in a 4 1/2" square format to the box and call the contents auto parts.Went from AZ to ME no problemo. Both my Fury and my Dakota are R12 and I want to keep them that way.

View attachment 489638

View attachment 489639

View attachment 489640

That'll keep you cool for a long time!

 

[pomonamissel]

well if you like those prices , go for it i'll stick to my 20 bucks a can duracool .

 

[CBODY67]

A few things I noticed when seeking to buy R-12 when it was still around. First thing is that the orig 1lb can size can hold less than 1lb of R-12, but the dialog on the can should state how many ounces of gas is in the can, as produced. They can look like 1lb cans, but only have 10 ounces of gas in them, for example,

On the last day that buying R-12 was legal, I bought some at work for my stash. When I went to check on them about 2 yrs later, they were "light" (i.e., empty). Leaked from the crump on the seal, I suspect. So much for that bright idea!

FWIW,
CBODY67

 

[Mr onetwo]

Don't care to use propane/iso butane based refrigerants in my vehicles.In a properly sealed and maintained system R12 is best for compressor life and efficiency. Here is a good breakdown on this subject... Duracool-12A (TM), Envirosafe (TM), RedTek (TM), FrostyCool (TM) AKA Hydrocarbon AC Refrigerants

 

[Mr onetwo]

My '92 Dakota at 204,000 miles is all original R12 and has never been opened.Still works perfectly.

 

[pomonamissel]

well the durcool runs about the head pressures of your r12 . and your right a sealed system has no worries .

 

[Dan Scully]

I picked up a a/c machine pretty reasonable , it can recover , store and recharge. I ratholed about 120# of R12 and about the same of 134. So I think I,am good for a bit .