R12 Guage set on R134a?

[RichNJKubota]

I know this is not a tractor related question but I figure it's the best place to ask.
I'm putting a new AC system in an old car I have and I'm using R134a. The guage set I have is for R12. Can I use this guage set on R134a also? I don't see why not. But I thought I'd ask first.

Thanks in advance,
Rich

 

[Dusty]

I am very familiar with these type of conversions. Depending on how old a car it is, depends on whether you should use R-134 or stay with the R-12. The molecules in R-134 are much smaller and will migrate out of the rubber hoses on many of the old cars, so while it is less expensive to use R-134, you will not get the cooling or long lasting charges.
As to the question about the gauges, I believe that the gauges themselves are the same, but he hose fittings at the ends where they attach to the system are different. Once you convert a R-12 system to R-134, you can't go back. You need to install adapters on the old fittings and they can't be removed once installed. They are what is know as a one way thread. It is barbed, so if you try to remove it, it will just dig in deeper to the original fitting. Total replacement of the hoses is the only way to go back. The price of R-12 has dropped in recent years, so I would stick with that unless you are quite certain that your car is going to accept the R-134 and not have problems. I won't even change over my 1978 Cadillac from R-12, because the small savings isn't worth the aggravation that I have known others to have. Only after the entire stock of R-12 is depleted, will most serious hobbyist convert. I see it all the time on eBay and it sells for between $10 - $30 per can. If you want to get the certification to buy it, you can take the test on line with the EPA. The test has all the study materials on line also. It isn't that hard to do. As the GEICO ad says, "even a cave man can do it".
Dusty

 

[KICK]

since you cant buy R 12 unless you have a license and it sounds like you don't, and you also want to do it yourself you are going to have to stick to the 134a.

dusty sed the EPA test was easy, I dont remember the one I took being EZ. I am EPA 608 certified type II and universal .

if you dont haVe recovery equipment you aren't legally allowed to handle refrigerant , 134a is still available over the counter.

yes you can use the gages if you have them, they will still hook to your old vehicle. problem is they wont hook to any 134a can or bottle and you can buy and adapter for your gages.

you can charge with a can apapter straight to the system.

134a runs at similar pressure to R12. does it leak faster?? I dont think so, I converted several of my vehicles and dont recall having to top them up any more frequently than I topped up an R12 system.

best way to retrofit a system is to dismantle and flush it and put int he correct oil befor eyou make the changeover.

 

[RichNJKubota]

Thanks for your replies. To clarify - this is a new system. All new parts, hoses, etc. Many parts are custom made to be like the originals. I've converted the factory AC systems on these cars before to R134a and they work fine. Can't tell the difference between R12 and R134a.
But I've only used the charging can and hose from the auto parts store when I did the conversions. I'd really like to keep an eye on the high side pressure while chraging just to be safe. That's why I'd like to use my R12 guage set.

Thanks,
Rich

 

[Dirthog]

You cannot use R12 gauges on R134 they are different the R134 runs at higher pressures also the fittings on the manifolds are different and they do make fittings to connect them just for that reason

 

[grunewald]

R12 and R134A are very close to same pressure and temp. The gauges will be OK, just the hose fittings are different. If you do use the R12 gauges, be sure to clean the oil out as best you can. R12 uses mineral oil, R134A uses POE oil, not compatible, will cause problems on very small system such as a car or truck.

 

[Dirthog]

I have been ASE certified to work on air cond systems in construction equipment since 1992 and haven't heard of that. Don't know where you you are buying gauges but the three sets we have at are dealership are different they are higher pressure for the R134 than the R12 they are a couple of years old though so maybe the new ones have changed not sure Also the new equipment that we sell and service the pressures are higher on the R134 systems than they were on the R12 more so on the high side especialy in hotter weather.

 

[KICK]

this would be comparison of pressure /temperature relationships between R12 and R 134a for those who care..


http://www.fjcinc.com/pdffiles/tprc.pdf

 

[shaley]

And if you want some real cooling cpacity replace the R12 with LP gas. Works great but I wouldn't smoke while I drive.

 

[KICK]

Also the new equipment that we sell and service the pressures are higher on the R134 systems than they were on the R12 more so on the high side especialy in hotter weather.

pound for pound, R134a doesn't have the same amount of heat energy as r12 and you see it on the hi side in conditions with low air flow over the condenser.

its fairly common to have complaints about the 134 systems not cooling very well if vehicle is idling , ie low compressor speed or when they dont have much air flow over the condenser , as compared to a r12 system. you see hi head pressure more commonly in those cases.

in cars 134a works fine as long as you have some speed to move air over the condenser but if you're stuck in traffic, it loses some of its efectiveness.

interesting how a/c works from a scientific perspective, its not like you are making the air colder by blowing it over a cold spot , more like you are taking the heat energy that is being absorbed in the evaporator when the refrigerant is boiling, and moving that absorbed heat out into the atmosphere at the condenser.